Temperature Instrumentation

Temperature instrumentation in this category covers RTD probes and thermometer assemblies, head-mount, rail-mount and field-mount temperature transmitters, wireless units, safety temperature limiters and dry block calibrators. The products come from JUMO, WIKA, Rosemount, Endress+Hauser and ABB, with further items from other makers listed below. Seven Star LLC supplies these temperature sensors and transmitters from Muscat to process plants, utilities and building-services contractors in Oman and the GCC.

Temperature sensors, transmitters and calibrators listed

• RTD temperature probes: screw-in, mineral-insulated and thermowell-mounted assemblies from JUMO, WIKA, ABB and Rosemount.
• Temperature transmitters with 4-20 mA, HART or wireless output from Rosemount, Siemens and Yokogawa.
• Safety temperature limiters and monitors from JUMO.
• Humidity and temperature sensors for ducts and rooms, with Siemens, Vaisala and Industrie Technik in the list.
• Dry block calibrators from Isotech for checking sensors on site.
• Further items from Moore Industries and Honeywell.

Choosing an RTD, a thermocouple and a temperature transmitter

RTDs are the usual choice for moderate temperatures where accuracy and stability count. Thermocouples cover higher temperatures and tolerate vibration better. For an RTD the wiring matters: three-wire and four-wire connections compensate for lead resistance, and four-wire gives the best result. The sensor normally sits in a thermowell so it can be changed with the process running. Thermowell length, shape and material follow the line size, velocity and fluid, and on fast-flowing lines a wake frequency calculation to ASME PTC 19.3 TW is commonly required. A transmitter in the connection head converts the sensor signal to 4-20 mA close to the source, which avoids long runs of sensor cable. Ex ia or Ex d versions are used in classified areas.

What to send for a quotation

For a sensor, send type and class, number of elements, insertion length and diameter, process connection, thermowell material and dimensions, head type and temperature range. For a transmitter, send input type, range, output, mounting style and approvals. A full model code is the best reference. We check it against the manufacturer documentation and propose the manufacturer’s successor for obsolete models.