Electronics International CA-1 - Manual (Page 17)

14
TROUBLESHOOTING SUGGESTIONS
Because high reliability is designed into Electronics International’s equipment, there is no reason to put up with
poor operation. We have few problems with our probes, cables and units and installation is simple. Usually
fixing a problem is just a matter of inspecting the installation at a few key points.
Strategy:
If you have more than one problem, FIX ONE PROBLEM AT A TIME. Trying to fix all of them at once
can be confusing and misleading. In many cases fixing one problem first will lead you to the solution for
fixing all of the problems. Therefore, take one problem on one channel and proceed with the following:
1. Instrument Check Out:
If there is an identical symptom on each channel, then the instrument may have a problem. But if even one
channel of the instrument is operating properly, the instrument probably does not have a problem. A good
method to test the instrument is to remove all the Extension Cables. Then look for a reading on all channels
to be near cabin temperature. The only inputs a unit requires to operate properly and measure cabin tempera-
ture is power (red lead) and ground (black lead). Check the power and ground leads for proper connection
(pull on the wire at each connector).
NOTE: Few problems turn out to be the instrument.
2. Probe Check Out:
There are two good methods of testing a probe. Perform one or both of the following:
A. A probe can be tested with an ohmmeter. Disconnect the probe from the Extension Cable. When
testing the resistance between the connectors, the probe should measure a “short” (less than 5 ohms).
When measuring from one lead (either lead) of the probe to the probe sheath (metal tip), there should be
an “open” (10k or greater).
B. Another method of checking a probe is to plug the suspected bad probe into a channel that is work-
ing properly. If the problem follows the probe, you have a defective probe.
3. Extension Cable Check Out:
With the Extension Cable connected to the unit, remove the probe from the suspected bad Extension Cable.
Set the unit to the proper channel and look for a near cabin temperature reading on the display. A very high
or low reading indicates a short to ground in the cable. Next, connect an ohmmeter, set to 10K range, to the
open probe ends of the suspected bad Extension Cable. Set the unit to the proper channel and look for a very
high (+ or -) reading on the digital display. A near cabin temperature reading or no change in reading
indicates an open in the cable or its connectors. Also, look for a reading on the ohmmeter around 12K ohms.
Most problems of this kind are usually one of the following: