A special type of temperature measuring device can be found in the remote thermometers. This device class is always used where a direct temperature measurement is possible, for example, a display is not feasible or not appropriate. Classic examples here would be mechanical engine temperature readings on tractors and electric temperature readings in normal vehicles. The same applies to a large number of machines and devices, where a measurement is necessary but the measuring point is not directly visible. In all these cases, the measurement must be made at the demand point, but the display can be made elsewhere.
There are different measurement options and display connection options. In the simplest case, the distance between the measuring sensor and the indicating instrument can be bridged by a capillary tube. Typical lengths are here a few inches to a few meters. The connection is made by a corresponding capillary tube. At the measuring point, a temperature difference then generates a pressure change, which is forwarded to the indicating instrument. There, the pressure change in a pointer works generates the corresponding movement on the scale.
Designs and measuring ranges
Remote thermometers are distinguished in the design and in the measurement method. With the types of construction one can differentiate between the classical mechanical pointer instruments and modern electronic digital displays. However, both technologies reliably and accurately display the measuring ranges. A standard remote thermometer consists of a complete instrument usually from the display instrument with glass capillary and a 1-meter long trunk with connector or threaded flange. The measuring range of such a remote thermometer can be between -30 ° C and + 400 ° C. The accuracy here is typically a good 1% of the scale value.
More modern designs come in digital design. These are then galvanically separated units, which usually consist of a display device and a measuring line with sensor. The temperature sensor is either installed in a device or flanged at a suitable location. The measured temperature value is then transmitted to the display unit via a very long measuring line or even wireless transmission. Digital remote thermometers can also communicate via the industrial I2C bus or via LAN connection.