Datasheet

J5 Not installed
Using a jumper across pins 2 and 3 of J5 bypass the MAX44248. The input signal range is
high and amplifier is not required.
J6 Not installed
J7 Installed
J8 Installed
J9 Installed
When not installed, this jumper’s subsequent pins can be used to measure the loop-
generated current.
Test Procedure
Relation Between Current Output (mA) and Temperature (°C)
The simplified correspondence between the generated output current and the temperature can be expressed by the following equation
below:
I
OUT
= 16mA[T°C/200°C] + 12mA
where T is the temperature sensed by the RTD and I
OUT
is the current loop.
If RTD Used
If RTD is used, test it at different temperatures, and observe the associated loop current.
At -100°C, the expected current is 4mA
At -50°C, the expected current is 8mA
At 0°C, the expected current is 12mA
At +50°C, the expected current is 16mA
At +100°C, the expected current is 20mA
If RTD Calibrator Used
If calibrator is used, test by varying the temperature value to change the resistance across the RTD calibrator terminals.
Observe:
At -100°C, the expected current is 4mA
At -50°C, the expected current is 8mA
At 0°C, the expected current is 12mA
At +50°C, the expected current is 16mA
At +100°C the expected current is 20mA
Detailed Description
The entire 4–20mA loop application consists of:
Smart sensor transmitter (process measurement field instrument)
Receiver (PLC)
The MAXREFDES15# contains the sensor analog front-end, the microcontroller, and the transmitter (Figure 2). The 4–20mA receiver can
be implemented by Santa Fe (MAXREFDES5#) and Campbell (MAXREFDES4#). Information about the Santa Fe and Campbell can be
found at
Santa Fe (MAXREFDES5#)
Campbell (MAXREFDES4#)
This document describes the operation of the smart sensor enabling the 4–20mA loop process.
The Smart Sensor Transmitter
The smart sensor transmitter block (see Figure 2) consists of:
Analog front-end
Microcontroller
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