Martel Electronics DMC1400 - Manual (Page 27)

5.2 Measuring current with loop power
To test a 2-wire, loop powered transmitter that is disconnected from
wiring, use the loop power function. This function activates a 24V
supply in series with the current measuring circuit. To use this option
proceed as follows:
1. Select [mA LOOP] as primary parameter in the upper display.
2. Connect the calibrator to transmitter current loop terminals, as
shown in Figure 17.
Figure 17. Connection Using Current Loop
5.2-1 HART™ Resistor Selection
The DMC1400 can be set-up so that the 250 ohm resistor required
for HART™ configuration devices resides inside the DMC1400.
Enabling the DMC1400's internal 250 ohm resistor eliminates the
need to manually add a series resistor during a HART™ calibration
process.
NOTE: When the DMC1400's internal 250 resistor is enabled,
maximum load driving capability drops from 1000 ohms @ 20mA to
750 ohms @20mA.
Enable/Disable Procedure
1. Remove the battery cover and remove the 2 screws that are
at the top of the case.
2. Remove the 2 screws on the bottom or lower portion of the
case.
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