Hart™ Resistor Setup; Basic Operating Modes - Ecom MA 400 Operating Instructions Manual

3.2 HART ™ Resistor Setup
The MA 400 incorporates an internal 50 ohm resistor to facilitate using a Rosemount 75
Communicator during calibration or installation of HART™ transmitters. The internal resistor takes the
place of the 50 ohm resistor normally installed during the use of the model 75 Communicator.
An internal jumper can be removed to enable this feature if desired. The unit is shipped with the jumper
in place. To remove the jumper open the case and refer to Figure  to locate the jumper, then pull off
the jumper to enable the resistor. The jumper can be stored outside of the unit or re-installed only
on one pin so that the circuit remains open.
Figure 2
Note: When the 50 ohm resistor is enabled the load driving capability is reduced from 100
ohms to 950 ohms. In most cases this should not be a problem when calibrating Non-HART™
compatible products.

4. Basic Operating Modes

The MA 400 offers 4 modes of milliamp operation and one voltage measure mode. The following
text and figures explain the various operating modes:
0
-J8 (HART™ JUMPER)
Remove Jumper to Enable HART™ 50 Ohm Resistor