card. By changing CH and the start and stop points in the loop
counter (line 1020), any block of voltages can be printed. The
PAUSE routine at line 3000 is only needed for the 134 and 141 A/D
cards. The Model 134 PAUSE need only be the 0.5 millisecond
settling time of the multiplexer. An empty loop can be used to
generate that short delay, but the loop counter value will depend
on the speed of your computer.
SECTION 3. TROUBLESHOOTING
A. Apparently meaningless numbers are produced:
1. Make certain that the Model 17B is plugged in to a live
outlet.
2. Connect the + and - wires leading to the A/D input together.
If the resulting reading is not within a few counts of zero,
either there is a miswire or the wrong channel is being
selected.
3. Check that none of the + or - input signals are outside the
allowable voltage range. Under some circumstances, other
channels can be affected by overranges.
4. A ground loop or missing ground wire can cause unpredictable
results. If there is a redundant ground wire, try removing
it. If you are using a wall socket ground for the external
ground connection, make sure that it is actually at ground
potential.
5. If more than one multiplexer, thermometer or other device is
connected to the output port, then all external devices must
be powered.
B. Some or all signals are of the wrong polarity:
1. If all the signals from a Multiplexer have the wrong
polarity then the wires connecting the Multiplexer output to
the Analog Interface input are crossed.
2. If one or several signals are of the wrong polarity, the
wires connecting to the Multiplexer input for the affected
channels are probably reversed.
C. Some or all signals show excessive scatter:
1. Make sure ALL input signals are within range.
2. A ground loop can cause excessive scatter. See A.4 (above)
or SECTION 1 of this manual for grounding procedures.
3. It is possible that the signals being measured are
oscillating. Try substituting a 1.5 volt battery or other
stable voltage source for comparison.
4. If the signals being switched are high impedance, some
errors may be introduced due to switching transients and
series resistance. Inserting a pause in the program between
setting the channel selection code and beginning the
conversion will help.