Martel Electronics 235 - Manual (Page 47)

The trip detect feature can utilize either the volts or 2-wire ohms input
terminals. If the alarm circuit has powered contacts, the volts input
should be used. If the alarm circuit has dry or non-powered contacts,
the ohms 2-wire input should be used. If the voltage input is used, the
maximum input voltage is 30 volts; however, the calibrator can only
detect changes in the 0-10 volt range. This is normally not a problem,
since the powered contacts typically switch between 0 volts and 24
volts.
A change of more than 1 volt or 100 ohms on the input is considered a
change of state of the alarm circuit.
Trip detect is enabled when the Ramp Function is initiated. The final
prompt when initiating the ramp is to enable or disable the trip detect
function. If you enable the trip detect function, the final prompt will be
to select ohms or volts and the input function will monitor for a
significant change in its input measurement. When a change is
detected, the output ramp is stopped and the current value is
displayed.
The ramp is controlled by the INC/DEC keys. The first press of the INC
or DEC key will cause the ramp output to assume the full scale or zero
value, respectively. The second press of the key will cause the ramp to
start and the input function to start monitoring for a change of state.
When the change of state is detected, the ramp is stopped. Pressing
the INC or DEC key again will restart the cycle.
To test the dead band of an alarm, first initiate a positive going ramp
using the INC key and record the trip point. Next initiate a negative
going ramp using the DEC key and record the trip point again. The
difference in the two recorded trip point values represents the dead
band of the alarm.
While the ramp is running and before the trip occurs, the input display
shows:
Input Functions
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