MODEL 134
             16-BIT FAST A/D CONVERTER

                                             LAWSON LABS, INC.
                                             3217 Phoenixville Pike
                                             Malvern, PA 19355

                                               610 725-8800
                                                    or
                                               800 321-5355

Rev. D

                       TABLE OF CONTENTS

INTRODUCTION                                        Page 2

1.  INSTALLATION                                    Page 2

2.  PERFORMING CONVERSIONS                          Page 3

3.  CHANNEL SELECTION                               Page 5

4.  CONTROL OUTPUTS & DIGITAL INPUT                 Page 6

5.  FAST SAMPLING SOFTWARE                          Page 7

6.  OPERATION FROM MACHINE LANGUAGE                 Page 11

7.  OPERATING SUGGESTIONS                           Page 12

8.  TROUBLESHOOTING                                 Page 13

9.  INTERNAL ADJUSTMENTS                            Page 14

10. SPECIFICATIONS                                  Page 15

WARRANTY                                            Page 16

INTRODUCTION

     The Lawson Labs Model 134 A/D card enables an IBM PC, XT or
AT computer to translate continuously variable analog voltages
into their digital equivalents of ones and zeros. It also
provides a means for the computer to turn external equipment on
and off. These functions are the basics of monitoring and control
systems. Both the analog inputs and the digital outputs are
protected against overvoltages.

     The Model 134 uses only four memory locations out of the 32
designated for a "prototype card." These four addresses can be
changed by altering the switch settings on the A/D card. This
arrangement minimizes the chance that there will be a conflict
between the Model 134 and any other peripheral card.

SECTION 1.    INSTALLATION

NOTE: Always handle circuit cards by the edges.

     There are four small switches in the upper left corner of
the Model 134. Switch #4 is unused. Place switches 1, 2 & 3 in
the OFF position. This will map your A/D card into input port
locations 796 through 799. If you have another special function
card in your computer which uses these locations, see Section 2
for alternate mapping.

     Static electricity can damage computer circuitry so care
should be taken to control static discharge. Turn off the
computer but do not unplug it. Remove the cover. First remove the
screw which secures the bracket behind a vacant slot. Then remove
the bracket. While holding the Model 134 in one hand touch the
computer's chassis with the other. This procedure will harmlessly
drain any static charge that may be present. Now insert the card
into the connector. Press down firmly to insure that the card is
seated and replace the screw in the bracket.

     Attach a pair of wires to pins 6 and 13 of the mating 15-pin
connector. The negative input is pin 13 and the positive input is
pin 6. The other end of the wires should connect to the voltage
being measured. A 1.5 volt battery is a convenient voltage source
for test purposes. For a battery or other floating voltage
source, a connection must be made between the negative input and
ground. The computer's chassis is the best ground for most
purposes.

NOTE: Strain-relief is recommended for all permanent wiring on
the connector. Otherwise, physical stress may cause the failure
of an electrical connection. The connector hood provided has a
built-in strain-relief clamp. 

FIGURE 1.    CONNECTOR PINOUT

PIN 8...CHANNEL 1+
                        PIN 15...CHANNEL 1-
PIN 7...CHANNEL 2+
                        PIN 14...CHANNEL 2-
PIN 6...CHANNEL 0+
                        PIN 13...CHANNEL 0-
PIN 5...CHANNEL 3+
                        PIN 12...CHANNEL 3-
PIN 4...GROUND
                        PIN 11...DIGITAL INPUT
PIN 3...GUARD
                        PIN 10...OUTPUT C
PIN 2...OUTPUT D
                        PIN 9....OUTPUT B
PIN 1...OUTPUT A

    Attach the connector and tighten the small screws that hold
the halves together. Replace the cover. Turn on the power to the
computer. If the power-on self-test (POST) does not behave
normally, turn off the computer and refer to the troubleshooting
section of this manual.

     Connect the plus and minus wires to the voltage being
measured. Make certain that the  voltage is in the +/- 5 volt
range. If the voltage source is floating in relation to ground,
e.g. a battery, also connect the minus side of the voltage being
measured to ground (not guard). For that ground connection, use
the ground pin on the Model 134's connector or, preferably,
chassis ground at the computer. If the computer chassis is not
accessable, use the ground pin of the grounded wall outlet where
the computer is plugged in. Remember that the positive and
negative inputs on the Analog Interface should both stay within 6
volts of ground potential. See FIGURE 4.

NOTE: For maximum reliability, connect all unused inputs to
ground.

SECTION 2.    PERFORMING A/D CONVERSIONS

     In the absence of other instructions, the A/D card will
measure the voltage at input channel #0. Because the wires that
you attached are connected to input #0, we need not concern
ourselves with the channel selection process at this time. In
essence, one INPut instruction begins the conversion. 72
microseconds later the answer is stored on the Model 134 where it
remains until it is read with two INPut instructions, one for
each byte of the result.

     The Model 134 uses four port addresses. Writing to any of
those addresses sends information to the card. Three of the
addresses are for reading information from the card. If your
computer contains other special-purpose cards, the possibility of
port address conflict arises. Compare FIGURE 2 with the
documentation of other special-purpose cards present and select
switch settings that avoid port conflicts.

FIGURE 2.    DIP SWITCH SETTINGS

SWITCH POSITIONS          ADC            ADDRESSES
#1    #2    #3          ADDRESS            USED
--------------------------------------------------
ON    ON    ON            769             768-771
OFF   ON    ON            773             772-775
ON    OFF   ON            777             776-779
OFF   OFF   ON            781             780-783
ON    ON    OFF           785             784-787
OFF   ON    OFF           789             788-791
ON    OFF   OFF           793             792-795
OFF   OFF   OFF           797             796-799

     An OUT statement to any of the four addresses in the range
is equivalent. Reading the lowest port in the range provides
status information. Reading the next address (ADC) yields the
less significant byte of the answer. Read the third address for
the more significant byte of the answer. Reading the highest port
address has no effect. Change the ADC (Analog to Digital
Converter) address in line 10 of the following BASIC program if
an alternate switch setting is used.

  10 ADC = 797
  20 X = INP(ADC): REM start conversion
  30 COUNT = INP(ADC + 1) * 256 + INP(ADC)
  40 VOLTS = (COUNT - 32768) * 1.52588E-04: REM scale
     in volts
  50 LOCATE1,1: PRINT USING "##.####"; VOLTS
  60 GOTO 30

      Line 10 assigns a variable name to the port address. Line
20 begins the conversion. Line 30 reads the raw count which is an
integer between 0 and 65535. Notice that the more significant
byte of the answer (ADC + 1) must be read first because reading
the low byte starts a new conversion. Line 50 displays the result
and line 60 repeats the process.

     RUN the program. (Use Ctrl Break to exit.) The voltage
should appear in the upper right-hand corner of the screen. The
Model 134 Analog Interface resolves 0.153 millivolts. A fresh D
cell should read about 1.5 volts. With reasonably short wires, or
with shielded wire, expect to see about +/- 1 count (.153
millivolts) of scatter. There is virtually no filtration in the
Model 134 so any noise on the input will appear as variability in
the readings. Connecting both of the input wires to ground will
cause a potential of zero volts. The reading with the input
shorted should be within a millivolt of zero (32768 counts). It
is normal to see slightly increased scatter at zero volts. An
open circuit will read unpredictably. An overvoltage will read
4.9999 or -5.0000. The input channels are protected against
transient overvoltages of up to 125 volts and continuous
overvoltages of 40 volts. Reverse the wires and note the polarity
change. The plus sign is implicit and does not appear on the
screen.

     The conversion itself takes 72 microseconds. Reading the low
byte of the answer also initiates a conversion. In the above
program example, line 20 need only execute once because a new
conversion begins each time the low byte is read in line 30. In
BASIC, and in all but the fastest computer languages, the
conversion will be over before the answer can be read. Routines
that take advantage of the Model 134's speed must be written in
fast languages. Those routines poll a status byte at address
ADC-1 to determine when the conversion has been completed.

SECTION 3.    SELECTING OTHER INPUT CHANNELS

     First connect the other voltage to be measured to an unused
pair of input pins on the Model 134's connector. See Figure 1.
The four available channels are numbered 0 through 3. To select a
channel, substitute the channel number to be selected for the "N"
in this instruction.

        OUT ADC, 16 * N

     Channel 3 could be selected using the instruction OUT ADC,
48 or OUT ADC, 16 * 3.

    Here is a sample routine which will measure the voltage at
each channel and print the data. It is also on the support disk
called DEMO134.BAS.

  10 KEY OFF
  20 CLS
  30 INPUT "Enter ADC (check your manual) "; ADC
  40 IF ADC < 769 or ADC >979 THEN PRINT
     "769 <= ADC <= 797": GOTO 30
  50 STATUS = ADC - 1
  60 CLS
  70 LOCATE 24,30: PRINT "Press Esc to exit"
  80 LOCATE 5,1
  90 FOR CHANNEL = 0 TO 3
  100 OUT ADC, CHANNEL * 16: REM select channel
  110 X = INP(ADC): REM start conversion
  120 COUNT = INP(ADC + 1) * 256 + INP(ADC): REM read card
  130 VOLTS = (COUNT - 32768) * 1.52588E-04: REM scale
  140 PRINT "Channel "; CHANNEL; " counts = ";
  150 PRINT USING "#####"; COUNT;
  160 PRINT, "voltage =";
  170 PRINT USING "##.####"; VOLTS
  180 NEXT CHANNEL
  190 PRINT: PRINT "Digital input is ";
  200 IF INP(STATUS) AND 128 THEN PRINT "OFF" ELSE PRINT "ON "
  210 GOTO 80

     Running the DEMO134 program with no connections made on
channels 1 through 3 will do no harm. However, the data from
those channels will be meaningless. Make a back up copy of the
support disk. Start BASIC or BASICA and put the working copy of
the support disk in drive A and type RUN "A:DEMO134". Provide the
ADC address when prompted. You will see the raw count and voltage
at each of the channels displayed on the screen. The current
status of the digital input is also displayed. See the next
section for a detailed description of the digital input.

     The FOR NEXT loop from line 90 to line 180 steps through the
channels and displays the readings. Notice that the conversion is
explicitly started in line 110. This step makes it clear that the
answer obtained in line 120 came from the input channel selected
in line 100. Notice that after the program has run, channel 3 is
still selected. Turning the power off and on or OUT ADC, 0 will
reselect input channel zero.

SECTION 4.    USING THE CONTROL OUTPUTS & DIGITAL INPUT

   There are four optically isolated output lines on the A/D
card. These are intended primarily for expanding the number of
input channels using an external multiplexer. Any channel can be
expanded to 16 channels with an external multiplexer. The
optically isolated control lines prevent ground loops from being
formed. Configurations of up to 64 analog inputs are possible
with four Model 17 Multiplexers. The outputs can also be used for
digital control. Think of each one as a contact closure to guard.

     The output port has the same address as the input channel
selector. The lower four bits appear, optically isolated, at the
connector. A number from 0 to 15 sent to port ADC will appear on
the output lines, coded in binary. The instruction OUT ADC, 3
will cause outputs A and B to become active. Below is a list of
codes and the corresponding active outputs. Note that the
sequence is that of counting in binary. 1=active.

FIGURE 3.    OUTPUT CODES

  CODE           OUTPUT  D C B A

   0                     0 0 0 0
   1                     0 0 0 1
   2                     0 0 1 0
   3                     0 0 1 1
   4                     0 1 0 0
   5                     0 1 0 1
   6                     0 1 1 0
   7                     0 1 1 1
   8                     1 0 0 0
   9                     1 0 0 1
   10                    1 0 1 0
   11                    1 0 1 1
   12                    1 1 0 0
   13                    1 1 0 1
   14                    1 1 1 0
   15                    1 1 1 1

   If it is necessary to alter the output code without affecting
the input channel selection, the input selection code should be
added to the output code. For example, to select input channel 1
with output code 15 use OUT ADC, 16 + 15 or OUT ADC, 31.

     Electrically, each output line is the collector of an
optically coupled NPN transistor whose emitter is connected to
guard. Note that guard is not connected to ground on the Model
134. The guard is usually connected to the external device's
ground. Each output line can drive two low-power TTL loads or
many CMOS loads. An external pull-up resistor (from the collector
to the external positive supply) must be used. Typically, 20 K
ohms for low-power TTL or 47 K ohms for CMOS is appropriate. When
the output code is 0 all four phototransistors are off and no
current is drawn through the transistors. If the input to an
inverting buffer is connected to output line A (with the
appropriate pull-up resistor), the input level is forced high by
the resistor so the buffer output would be 0. If the output code
is 1, the A transistor will turn on and pull the buffer input to
a logic level 0. The buffer output will then be a logic level 1.
     The digital input can be a contact closure to ground or a
TTL or 5-volt CMOS logic level, active low. This line reads the
digital input.

     IF INP(ADC-1) < 128 THEN PRINT "ON " ELSE PRINT "OFF"

SECTION 5.    USING THE FAST SAMPLING SOFTWARE

     The FASTSAMP software is unprotected and fully listable. It
can function as a self-contained data acquisition system or it
can be included, all or in part, in your BASIC programs. FASTSAMP
is written in BASIC and machine language. Most of the BASIC code
is the input section which allows you to define a sample run.
That definition is contained in an integer array called SAMPLE%.
The array is dimensioned at 84 elements. The machine code
occupies the top 768 bytes of BASIC'S 64K address space. The
address of SAMPLE%(1) is passed to the machine code in a CALL
instruction and the specified pattern of data points are stored
in high memory. The data can be moved to a disk as a sequential
text file suitable for importing by Lotus 1 2 3 (reg. trademark)
or can be saved as a binary image using the BSAVE command.

     Load BASIC or BASICA and type RUN "FASTSAMP". FASTSAMP
begins by loading two binary files from the disk, SAMP and
SAMARRAY. FASTSAMP will look only in the default directory for
those files. SAMP is the machine code itself and SAMARRAY is a
bit image of the SAMPLE% array. The last SAMPLE% array that was
saved on the disk will be the starting point for the session.
FASTSAMP does not do comprehensive error trapping so double check
your entries. If you mis-enter something, keep going and you will
be given a chance to correct the mistake. You will be prompted
for the following information:

1)  IN FASTSAMP, sampling runs are timed and fine-tuned for
accurate sampling rates. Under most circumstances, 1% timing
accuracy can be obtained. If you are running FASTSAMP for the
first time on a particular machine, or if the clock rate has been
changed, then select T for new timing. When you select new
timing, the length of one interchannel delay count is
established. You will normally press space to continue. Then, the
last calibration (stored in the SAMARRAY file) is used for timing
the interchannel delay.

2)  Enter ADC (see Section 2).

3)  The Model 134 can run at double speed at half the resolution.
Select 8- or 16-bit resolution.

4)  The interrupts may be disabled during the sample run.
Interrupts can cause irregularities in the sampling interval. If
the interrupts are disabled functions running in the background
such as ON TIMER GOTO will be disrupted. Also, the time of day
clock doesn't run when the interrupts are off.

5)  The starting address for the memory data table has to be
entered next. You need at least 128K of main memory and you must
know if anything is residing in high memory, a virtual disk
program, for example. Also be aware that some DOS commands like
MODE and PRINT cause DOS to allocate more memory. You should be
able to determine where the beginning of free RAM is by loading
BASIC and typing

   DEF SEG = 0: X = PEEK(&H511) * 256 + PEEK(&H510):
   PRINT X * 16 + 65536: DEF SEG

The first free address above BASIC's 64K space will be printed.
Not all BASICs update these memory locations. You may need to use
other methods to determine where free memory begins in your
machine. The upper limit for the data table will be the amount of
installed memory up to 655360 (640K). That means that sampling
runs of 270K 16-bit data points can be accommodated. The starting
memory address for the data table is always a multiple of 16. If
you enter a number that isn't a multiple of 16 the remainder will
be discarded.

     FASTSAMP does not check to see if the data will overwrite
BASIC or portions of the operating system. If your data table
includes non-existent RAM, no harm will be done but the data
stored there will be irretrievable.

6)  For multiple channel routines a brief delay after switching
channels may be desirable. This pause allows very high impedance
voltages to settle to 16-bit accuracy. If you don't need all the
available speed, a delay count of 1 is recommended. If you are
using an external multiplexer, a delay of at least 0.5
milliseconds will be needed for maximum accuracy. Delay counts
above 32767 will cause an OUT OF RANGE error.

7)  Up to 256 samples can be averaged to obtain each data point.
This feature is useful for compressing slowly changing data and
for noise suppression. Note that very noisy, highly averaged
data, even if it is reproducible, may suffer decreased accuracy.
The number of samples to average must be a power of two. If a
number besides 1, 2, 4, 8, etc. is entered, a power of two will
be proposed.

8)  From 1 to 64 data points can be taken at each scan. The data
points can be taken in any sequence. For example, a scan could
consist of channel 3 being sampled 63 times followed by channel 0
being sampled once. At this point, enter only the number of
points per scan desired. After the number of data points per scan
has been entered, if anything has been changed (or if you just
started FASTSAMP) there will be a pause of about 15 seconds while
timing is determined. If one scan per second or faster cannot be
achieved, you will be asked to reduce the averaging or
interchannel delay.

9)  Enter the scanning rate in scans/second. Rates from .5 to
22,000 scans/second are possible. Normally rates slower than one
scan/second can be programmed directly (or use Lawson Labs PC64
software). If you enter a rate faster than the maximum attainable
for the sampling run you have defined, the highest allowed rate
will be displayed. FASTSAMP will change the rate you enter to the
nearest nominally available rate. Remember that interchannel
delays and averaging will lower the maximum scanning rate.

10)  Next enter the number of scans per sample run. If you're not
sure there is sufficient memory, proceed and let the program
calculate the end of the data table for you. After the number of
scans is entered, a review of the sampling run is presented. If
everything is correct answer "Y" to the prompt. If you answer "N"
another pass through everything is offered. Take particular note
of the data table start and end addresses. Make sure the end
address is not above 655360. Also note the sample run duration so
that you don't give up too soon on a long sampling run.

11)  After the sample run has been defined, you will be given the
option of verifying the timing. If anything bearing on the timing
of the sampling run has been changed, the timing should be
verified. If the sampling rate selected cannot be achieved within
1%, then a possible rate will be proposed. Otherwise, the timing
will be fine-tuned and you will proceed.

12)  If you want to load a previously BSAVEd data file answer "Y"
to the prompt. Note that the file to be loaded should have the
same number of points per scan and the same number of scans as
the current configuration. You will be prompted for the file
name. Skip to paragraph 14.

13)  Finally, the control code for each data point must be
entered (see Sections 3 & 4). If no external multiplexer or
control device is in use, then codes 0, 16, 32, & 48 will select
the four channels. If a Model 17B multiplexer were connected to
channel 2, then control codes 32 through 47 would select the 16
multiplexed channels. FASTSAMP displays each control code in
turn. If a proposed control code is correct, just press RETURN to
leave it unchanged. You will be given a chance to review or
revise the control codes after the whole scan has been defined.
Holding down the RETURN key will speed you through the review.

14)  If you don't want the sampling routine to execute, Press the
Esc key at the prompt. Otherwise press SPACE to begin sampling.
You may want to save your sampling run definition on the disk
before attempting to execute it. To do that, press Esc now and
skip to 16.

15)  If the "Sampling complete" message does not appear after the
sampling duration has elapsed, you have probably overwritten some
vital memory contents. If Ctrl-Alt-Del does not answer, you will
need to resort to the power switch or reset button. 

16)  If you want your data saved as a text file answer "Y" to the
prompt and provide the full file name specification including the
drive designation and file name extension, if any. If you want to
import your data into Lotus 1 2 3 (reg. trademark) you will need
to use a .PRN extension. The text file is a standard ASCII
sequential file with one entry for each data point and a new line
for each scan. Versions vary, but Lotus may allow as few as 34
data points/scan and as few as 2048 scans/data run. The text
files can also be read from a separate program or you can use the
DOS TYPE command to review the data. With the DOS prompt, typing
          TYPE filename > LPT1
will send the whole file to your printer.

17)  The raw data will now begin scrolling down the screen.
Remember that 0 counts = -5 volts, 32768 counts = 0 volts and
65535 counts = 4.9999 volts. Press SPACE to pause or to skip the
rest of the data. Press SPACE again to continue scrolling or
select the exit or the restart option.

18)  You will be offered a chance to save the sampling run
definition on the disk. If you save it, the previous definition
will be overwritten and the next time you run FASTSAMP you will
start from the current status. If you don't save it, once you
exit the program your current definition will be gone. 

19)  Select the restart option to take more data or to change the
sample run. If you want to save the data as a binary file, you
should exit now and issue the BSAVE command(s) from immediate
mode. To BSAVE your data, first type DEF SEG = X/16 where X is
the start of your data table. Then type BSAVE filename, 0,
TABLELENGTH. Use DEF SEG to restore the default data segment. If
your table is more than 64K long you will need to save it in
blocks of 64K or less. Use 65536 instead of TABLELENGTH in the
first BSAVE then type DEF SEG = X/16 + 4096. Repeat the BSAVE
changing the filename to indicate part 2. The third DEF SEG would
be X/16 + 2 * 4096. Continue until all the data is saved.

    If you want to incorporate a sampling run into a BASIC
program of your own, it isn't necessary to include all of
FASTSAMP in your program. Instead you can generate and save the
SAMPLE% array using FASTSAMP, then BLOAD that array and the
machine language driver into your application program. The uses
for all the elements in the SAMPLE% array are described in the
FASTSAMP program listing. There should be enough information
there for you to make small changes in the sample run by changing
the SAMPLE% array in your application program. You may want to
use the digital input or an extra input channel as a trigger for
synchronizing the sampling run.

     There are several things to remember when incorporating
FASTSAMP into your program. Start your program with these lines:

  10 CLEAR , &HFD00
  20 DEF SEG
  30 BLOAD "SAMP", &HFD00
  40 DIM SAMPLE%(84)
  50 BLOAD "SAMARRAY", VARPTR(SAMPLE%(1))
  60 SBRT = &HFD00

     The CLEAR statement must set aside at least 768 bytes for
the driver. The first BLOAD puts the machine language driver in
that reserved space. After the SAMPLE% array has been dimensioned
the second BLOAD assigns the values to the array that had been
previously assigned and saved by FASTSAMP. Note that those files
are assumed to be present on drive A. To begin a sampling run,
start with a DEF SEG to make certain that the default segment is
current, then use

       CALL SBRT (SAMPLE%(1))

to begin sampling. The data can be retrieved by setting DEF SEG =
X/16 (where X is the start of the data table) and PEEKING at the
data. The first answer would be PEEK(0) + PEEK(1) * 256 for a
16-bit routine.

SECTION 6.    USING MACHINE LANGUAGE

     Using the Model 134 from machine language requires checking
the status byte to determine if the conversion is complete. The
least significant bit of the status byte is set to one by a start
conversion and resets to zero after the high byte of the answer
is ready (36 microseconds after the start of the conversion). The
high byte can be read while the low byte is in progress without
disrupting the conversion. The next least significant bit of the
status byte also goes high when the conversion starts. That bit
is reset when the entire conversion is complete.

     Assume the DX register contains ADC. The normal sequence to
read the card would be:

      IN AL, DX     ;Start conversion
      DEC DX        ;Point DX at status
TST:
      IN AL, DX     ;Read status
      AND AL, 02    ;Mask conversion complete bit
      JNZ TST       ;Wait for complete conversion
      INC DX        ;Point DX at ADC
      IN AX, DX     ;Read both bytes

Remember that the IN AX,DX starts a new conversion. If you want
that next conversion to be at a different input channel, the new
control code should be output just after the conversion
completes. 

     For 8-bit resolution, the AND statement should read AND AL,
01. The 8-bit answer will then be loaded into the AH register.
The conversion started by the IN AX, DX command will yield a
valid answer even though the previous conversion was still in
progress when the start conversion was issued.

SECTION 7.    OPERATING SUGGESTIONS

     The Model 134 A/D card features fully differential inputs. A
basic understanding of differential measurements will help you to
use your card to best advantage. The plus and minus input pins
should be wired directly to the voltage being measured. In this
way, it is assured that the only current flowing in the wires
will be the input current of the A/D converter. Because the wires
have finite resistance, any current flowing will cause a voltage
drop and a corresponding error. The A/D card requires a
vanishingly small input current so the error caused by even very
long wires is negligible. For proper operation of the Analog
Interface it is necessary that the positive and negative inputs
both be within 5 volts of ground. For a floating voltage source,
this is generally accomplished by connecting a third wire between
the computer chassis and a ground terminal at the source of the
measured voltage. Ground currents may flow in this wire, but the
resulting voltage drop will not cause a measurement error. If the
source of the voltage being measured is a line-connected device
with a three-pronged plug, its output voltage may or may not be
referenced to ground. In that case, try with and without a ground
connection for best performance. Redundant grounding can cause
ground loops. Ground loops can cause unpredictable behavior.

FIGURE 4.    TYPICAL INPUT CONNECTIONS

     The Model 134 filters very high frequency noise only. Any
noise below 1 megahertz will cause increased scatter. If your
voltage source is noisy, scatter will result. Best results are
obtained with filtered, buffered voltages. Electrical noise
travels through the air and can be picked up by interconnecting
wires. The first defense against noise is shielding. Use shielded
wire with the shield connected at one or both ends to ground.
(See above). The lower the impedance of the voltage source, the
less susceptible the wiring will be to electrical noise. If noise
problems persist, try to locate the source of the interference
and shield it. Electric motors, electric heaters and flickering
fluorescent lights are potential sources of interference.

SECTION 8.    TROUBLESHOOTING

GENERAL:

     If the A/D converter appears not to be working, first check
all external wiring and all port addresses. Double check the
switch settings on the Model 134. Be sure that all input voltages
are within range. If another special function card is present,
check for conflicting port addresses. Also, try adding a wire
from the negative input to chassis ground. Make certain you are
not using guard instead of ground.

1:  Results seem to be meaningless numbers

     The most likely culprit is a loose wire or an input with
nothing attached. Try connecting the + and - inputs to ground. If
the voltage does not read close to 0, the problem is in the wires
themselves or in the channel selection. Check that the program
has been correctly entered.

2:  The answers are consistent but wrong

     The ADC port address is wrong or in conflict with another
card. Also, make sure all inputs are within range.

3:  Readings show excessive scatter

     First check for proper grounding. If there is no connection
between the negative input and ground, try one. If there is such
a connection, try removing it.

     If the card reads a 1.5 volt battery properly but still
returns widely varying numbers when measuring a voltage, the
voltage could be oscillating or noisy. If you check the voltage
with another voltage-measuring device remember that some meters
will average out oscillations or noise to produce a steady
reading. Try switching to an alternating current scale. If you
get a reading the voltage is certainly unsteady. The A/D card
will filter out noise above a megahertz but any noise below those
frequencies will cause increased scatter.

SECTION 9.    INTERNAL ADJUSTMENTS

     The two adjustments on the Model 134 are gain and offset
controls. The gain adjustment varies the reference voltage used
during the A/D conversion. The long-term stability of the initial
calibration is excellent. If you decide to alter the original
gain setting, be sure your voltage reference or test meter is
sufficiently accurate and has been calibrated recently. Remember
that if you change the gain setting you may not be able to
restore the converter to its original accuracy.

     The adjustments are at the top edge of the A/D card at the
rear. The potentiometer nearer the front of the computer is the
offset adjustment. It is best to make any adjustments with the
card at its normal operating temperature. First set the offset
for zero volts with both inputs connected to ground. Then adjust
the gain to match a known voltage.

TYPE:                successive approximation

INPUT
RANGE:               +4.75 to -5 volts guaranteed
                     +/-5 volts typical

RESOLUTION:          0.153 millivolts

ACCURACY:            0.03% of full scale (0.01% available)

INPUT
IMPEDANCE:           10000 megohms

CONVERSION
TIME:                72 microseconds at 16-bit resolution
                     or 36 microseconds at 8-bit resolution

MAXIMUM SAMPLE
RATE:                12,000 samples/second at 16-bit resolution
                     22,000 samples/second at 8-bit resolution
                     (using included software)

ANALOG
INPUTS:              4 channels, fully differential
                     protected up to 125 volts transient
                     or 40 volts continuous

DC COMMON MODE
RANGE:               +/- 6 volts

DIGITAL
INPUT:               single-bit, TTL or 5 volt CMOS compatible

DIGITAL
OUTPUTS:             4 latched optically isolated lines
                     protected to 200 volts
                     each output will drive two low-power TTL
                     loads or many CMOS loads

TYPICAL POWER        +5v.......210 milliamps
CONSUMPTION:         +12v.......24 milliamps   (after warmup)
                     -12v.......18 milliamps

SIZE:                3.9 x 7.7 inches
                     0.625 inches maximum height

                     LIMITED WARRANTY

     The Lawson Labs, Inc. Model 134 Analog Interface is
guaranteed against defects in materials and workmanship for a
period of one year from the date of delivery. Products must be
returned to Lawson Labs for warranty service. Contact Lawson Labs
at 800 321-5355 for return authorization before returning
anything for service.

     The above warranty is in lieu of all warranties express or
implied. Lawson Labs will not be liable for indirect or
consequential damages caused by any defect in this product. Some
states do not allow the limitation of consequential damages, so
the above exclusion may not apply to you.