In-line temperature transmitters

08 April 2008

A unique, rapid and simple solution to convert to, or add 4-20mA loops using existing sensors in-situ without process downtime

Now it is simple and cost-effective to retro-fit 4-20mA temperature transmitters to existing Pt100 or thermocouple sensors without removing them from the process or having to replace them with alternative assemblies.

The unique, Labfacility ILTX in-line transmitter is a small plug-in module which simply connects to an existing or new insulated sensor without the need for a special assembly or connecting head. In many industrial and scientific applications where heavy duty housings are not required, the rugged ILTX provides a quick, convenient means of establishing a 2 wire transmission loop. It is ideally suited to light industrial use, laboratories, instrumentation departments, educational establishments, research facilities and R & D applications.

The ILTX can be used as a free-mounted unit or can be surface mounted via integral fixing lugs. Connections to it are made using miniature connectors which are polarized to prevent cross-connection and colour coded to suit the sensor types.

A key feature of the transmitter is the minimal-interaction span and zero calibration potentiometer action which is time saving and convenient when scaling or offsetting; an exceptionally wide range of adjustment is provided by the potentiometers to allow for easy re-calibration of the 4-20mA temperature range. For example, a type K thermocouple which has a working temperature range of 0 to 1100oC can be easily calibrated to operate between 0 to 600oC, where 4mA and 20mA represent 0 and 600oC respectively.

The compact, lightweight, potted module houses an accurate, stable, measurement circuit which incorporates automatic cold junction compensation for thermocouple inputs. Since the ILTX is designed to be connected to the extension cable which exits the temperature probe, particular attention has been paid to eliminating the effects of possible noise pick-up at the input. The 4-20mA loop powered transmitter provides an accuracy of ±0.2% of span for thermocouples type J,K & N and ±0.1% for Pt100 sensors. The output is directly proportional to the mV input signal for thermocouples and to the temperature input for Pt100 sensors.

The key benefit of using a 4-20mA interface between the sensor and the host measuring instrument is that long cable runs will not reduce the measurement accuracy. Compared with using thermocouple extension cables instead, there are significant cable cost savings since the 4-20mA loop requires only low-cost copper cable.

For multi-sensor installations, especially those using different sensor types, 4-20mA loops allow the use of standardized process indicators which can be simply configured to the appropriate temperature ranges e.g. 4-20mA corresponds to 0 to 1100oC for a type K sensor.

The ILTX is CE and RoHS compliant and is guaranteed for 2 years.

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In-line temperature transmitters

08 April 2008

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