Martel Electronics 135 - Manual (Page 56)

Calibration of an Alarm Using Ramp and Trip Detect
This example describes calibration of a current input alarm circuit. The
calibrator should be connected as shown in Figure 5. The connection to
the alarm contacts can be made across either the NO or NC contacts
since the calibrator is simply looking for a change of state.
This example assumes that the alarm should trip when the current
exceeds 12 mA and reset when the current falls below 11 mA.
Once the connections are made, the Volts input function and the mA
function should be selected.
1.
Press the RAMP key and enter 9 in response to the “starting
point” prompt. Enter 14 in response to the “ending point”
prompt. Enter 60 in response to the “time” prompt. This will
result in a Ramp step value of less than 20 microamps, which
should be suitable.
2.
Press the INC key to ready the ramp at its starting (9 mA) value.
3.
Ensure that the alarm is not already set. If it is, it may be
necessary to widen the starting and ending values and perform a
coarse calibration to bring it closer to calibration, then repeat the
procedure with the Ramp set to the closer limits.
4.
Press the INC key again to start the Ramp.
5.
Wait for the alarm to trip and the Ramp to stop. The input display
will show “tripped”, and the Ramp will be stopped.
6.
If the alarm trip point is not within the desired accuracy, adjust
the alarm set point and repeat from step 2.
Application Notes
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