Bench testing a CMCP420VT(T) is quite easy and can be
accomplished using a 24 VDC power supply and a DVM (Digital Volt Meter) in mA
(Amp) mode. Be sure that the fuse in the mA input of your DVM is good. Most
quality DVM’s have a 1 and 10 Amp selection. Select the lowest as you will only
be measuring to about 30 mA or 0.030 Amp. Be sure the power supply is wired plus
to plus and minus to minus to the CMCP420VT. The DVM can be inserted in series
in either leg.
The CMCP420VT requires a minimum voltage dependant on
resistance in the loop. If units locks at >21 mA voltage needs to be
increased by using an external +24 VDC power supply.
In the case of the CMCP420VT-T with Temperature the loop mA
is checked the same way, just move the wires to the temperature side of the
terminal. Heat the unit gently with a heat gun or your hand and mA output will
increase. Allow time for unit to heat soak and do not overheat.
The CMCP420VT will begin operation as soon as 24 VDC power
is supplied. Start up time is short but give the unit about 30 seconds for the
integrator to settle. At rest on a table or desk top the unit should read about
4.0 mA (0.004 Amp) depending on floor and table vibration. Tap the unit gently
against the table at a rate of a couple times per second. Increasing the force
of the taps will cause the unit to read over 20 mA (0.020 Amps).