4-20 mA current source

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  • Analog input testing
  • Actuator testing
  • PLC/DCS system software testing.
  • Loop checking
  • Alarm testing
  • PID controller testing

Various types available.

Panel mount types:

The 4-20 mA current source can be mounted in a panel. Specially when many signals need to be simulated panel-mounted 4-20 mA current sources are used for easy operation. This situation is typical for testing industrial automation systems such as PLC and DCS systems. Because these systems have many analog inputs for measurement of various signals from field instruments. Frequently used field instruments are temperature and pressure transducers. The 4-20 mA current sources can be used to simulate signals from these transducers. By simulating the signal the software used with the PLC and DCS systems can be verified for correct operation.

Boxed units:

  • Multi turn precision potentiometer
  • Indicator

When a single loop needs to be tested it is easier to use a hand-held, box mounted 4-20 mA current source. These current sources come with pluggable connectors. The pluggable connectors allow easy, fault free and fast connection to the loop which need to be simulated. Typical industrial connectors for 4-20 mA signals are M12, DIN 43650 and smaller variants of these connectors. 4mm Lab connections are also available. The 4mm banana connection is a standard connection used on multimeters and power supply's. The connection allows usage of standard test wires and crocodile clips to connect the 4-20mA current source to the loop.

Various ranges available.

The signal on a standard 4-20 mA loop will not drop below 4 mA or raise above 20 mA in normal operating conditions. However, modern transducers are capable of setting the current above 20 mA and below 4 mA to signal special conditions such as starting-up, failure, under and over-range conditions. When the 4-20 mA current source needs to be able to set the current above 20 mA and below 4 mA the range of the current source has to be extended. Many transducers comply to the Namur NE43 recommendation for the minimum and maximum current in the loop. 4-20 mA current sources with even larger range are also available. Be careful using these current sources as the higher current may damage equipment being tested.

Key benefits:

  • Simulate 4-20 mA signals.
  • Direct replacement for loop powered 2 wire- sensors
  • Exact and stable operation due to internal current source.
  • Very easy and intuitive operation. Turn clockwise to increase current, turn counter-clockwise to reduce current.
  • Tested to comply with various standards for Industrial equipment.
  • FCC and CE declaration of conformity available
  • World wide (express) shipping.
  • Delivery from stock.
  • Easy online ordering

Typical usage of the 4-20 mA current source:

When the field equipment or the industrial automation system such as a PLC, DCS system or PID controller is malfunctioning it needs to be repaired. The first step to do this is to isolate the problem. In this step each component of the system need to be tested individual. This prevents interference of other parts of the system. For this task a 4-20 mA current source can be used. Because a 4-20 mA current source allows manual setting of the current in the 4-20 mA loop, the correct functioning of the automation system and field equipment can be tested. This test eliminates the influence of other parts of the system. There are several selection criteria for the best 4-20 mA current source for your job.

Testing automation equipment:

For testing industrial automation equipment the sensor connected to the automation system can be replaced by the 4-20 mA current source. Before the sensor is connected, the connection to the automation equipment needs to be verified to determine how the 4-20 mA current source shall be connected to the system. A 4-20 mA current source can be connected in 2-wire mode or in 4-wire mode. When the 4-20 mA current source is connected in 4-wire mode, the unit will become a 4-20 mA generator. With the 4-20 mA current source the automation system functions such as alarm, control and logging can be verified. Sometimes it is necessary to simulate several 4-20 mA signals at the same time as the automation systems evaluates multiple measurement signals simultaneously. For this task multiple 4-20 mA current sources are required.

Testing field equipment

When actuators controlled by 4-20 mA signals need to be manipulated to verify the correct operation almost always a 4-20 mA generator (4-20 mA current source in 4-wire connection) is needed. Hence, most actuators do not supply voltage to the 4-20 mA loop. The 4-20 mA generator will set the current in the loop to invoke action on the actuator. The actuator can thus be verified for correct operation. Special attention is needed to make sure the 4-20 mA generator can drive the load from the actuator on the 4-20 mA Current Loop Tester

Technical information about usage of the 4-20 mA current sources


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