Using Isolated Measure Modes (Upper Display); Measuring Volts And Ma; Measuring Current With Loop Power - Ecom Instruments MCAL 4200 Instruction Manual

The custom function uses the Calendar-Van Dusen equation for outputting and measuring cus-
tom RTDs. The coefficient C is only used for temperatures below 0°C. Only A and B coefficients
are needed for the range above 0°C, so coefficient C should be set to 0. The R0 is the resi-
stance of the probe at 0°C. The coefficients for PT385, PT3926, and PT3616 are shown in Table
4 below.
RTD Range(°C)
PT385 -260 ... 0
PT385 0 ... 630
PT3926 Below 0
PT3926 Above 0
PT3916 Below 0
PT3916 Above 0
5. Using Isolated Measure Modes (Upper Display)

5.1 Measuring volts and mA

Use the following steps to measure the voltage or current output of a transmitter.
1. Select the upper display from the Main Menu.
2. Select the desired primary parameter to be measured. Connect the leads to the isolated
inputs of the calibrator, as in Figure 16.

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.
66
Table 4. RTD Coefficients
R0 Coefficient A
100 3.9083x10
100 3.9083x10
100 3.9848x10
100 3.9848x10
100 3.9692x10
100 3.9692x10
Figure 16. Isolated Input Connection
Figure 17. Connection Using Current Loop
Coefficient B
-5.775x10
-3 -7
-5.775x10
-3 -7
-5.87x10
-3 -7
-5.87x10
-3 -7
-5.8495x10
-3 -7
-5.8495x10
-3 -7
Coefficient C
-4.183x10
-12
—
-4x10
-12
—
-4.2325x10
-12
—