Martel Electronics 235 - Manual (Page 69)

Calibration of an Alarm Using Ramp and Trip Detect
This example describes calibration of a thermocouple input alarm
circuit. The calibrator should be connected as shown in Figure 5. The
connection to the alarm contacts on the alarm circuit 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 temperature
exceeds 300 degrees and reset when the temperature falls below 275
degrees.
Once the connections are made, select the thermocouple output
function with the appropriate thermocouple and temperature scale (°F
or °C) chosen from the menus.
1.
Press the RAMP key and enter 200 in response to the “starting
point” prompt. Enter 400 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 1 degree which should be
suitable. Next, “Enable” Trip Detect and select “Ohms” for the
input variable.
2.
Press the INC key to ready the ramp at its starting (200°) 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. Repeat the
procedure with the temp 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.
Application Notes
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