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:

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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