Sunday, September 11, 2011

Fluke Meters - Temperature

This section is about using Fluke meters to measure temperature. Please see themain guide for buying considerations and links to other guides about Fluke meters. Because E-bay limits the size of buying guides, I had to split my Fluke buying guide into sections.
What Meters Can Measure Temperature:
The advertising for many models does not mention temperature measuring at all.Other meters are advertised has having the ability to measure temperature, or, more confusingly, as having a "built in thermometer." This implies that you must have one of these meters to measure temperature, but this is not the case. Any meter can be used to measure temperature, the difference is whether or not an additional converter is required.
An electronic converter must be used to allow a temperature device to work with a meter to provide an acurate reading. Meters that have a "temperature feature" or "temperature measuring capability" have a built-in converter. The Fluke 16, 78, 87-5, 89, 187, 189, and 88-5 are just a few examples of meters with built in converters. There areothers. You can also get a separate converter that you connect to your meter. There are also temperature probes that have a built in converter. (converter is integral to the probe)
The advantage of a built-in converter is that the meter will show a "F" or a "C" on the LCD. Using an add-on converter, or a probe with built in converter will require you to set your meter to the proper function to read the converter's output (usually millivolts) and for you to realize, for example, that70 milivioltsmeans 70 degrees. (C or F, depending on your converter. Many are switchable.) To my knowledge, no Fluke meter has a built in thermometer - even meters that have temperature measuring capability (Built in converters) will need a separate probe or other temperature measuring device to measure temperature.
Temperature measuring devices: These can be simple probes that connect to an external converter or to a meter with a built in converter, or these can be more geplicated devices that contain their own built-in converter. Remember, there needs to be an electrical converter somewhere.If the converter is contained in the meter, you can directly connect a probe (many are thermocouples) to the meter and it will provide a reading in degrees directly.
AdaptorsMany thermocouples have a connector that will not physically plug into a Fluke meter (with built in coverter) or an external converter; these require a simple adaptor. (see pictures below) This adaptor has no electronic circuitry and does no conversion - it simply allows you to physically connect the probe to your meter. Be sure your probe and meter are gepatible - Fluke meters with built in converters (meters capable of measuring temperature directly) are gepatible with type K thermocouples. This adaptor will allow you to connect a thermocouple to a meter, but unless your meter has a built in converter, it will not measure temperature without an external converter. Picture shows a simple probe (no converter) that has a connector that will not physically connect to the Fluke meter. The physical adaptor is used to enable the probe to connect to the meter. Because there is no converter built in to the probe or adaptor, a fluke meter with temperature capability must be used. The probe must be a "type K" thermocouple.
Converters:If the meter does not contain a converter, you can still use it to measure temperature. You need either an external converter, or a temperature measuring device with a built-in converter.An external converter will connect to your meter and convert the temperature read by the probe into a millivolt signal. (If there are converters that convert temperature to another unit, I am not aware of them) Most converters output 1 millivolt per degree. (either Fahrenheit or Celsius, many can read both, depending on a switch setting) That means that if the temperature of what you are measuring is 77 degrees, you'll set your meter to read millivolts, and see 77 millivolts on your display. Be sure your converter and probe are gepatible. (eg use a "type k" thermocouple with a "type k" converter)Temperature measuring devices that have built in converters connect directly to the meter and give an output in millivolts, just as the external converters do. (Again, I am not aware of any temperature devices that provide any other type of output.) As with the converter, set your meter to millivolts and read the scale directly. Most of these probes output 1 millivolt per degree, so temperature can be read directly. One example of this device is the Fluke infra-red temperature probe. (pictured below) Fluke IR probe This probe provides an output signal in millivolts. Because the probe outputs 1 millivolt per degree, the temperature can be read directly. (30 millivolts = 30 degrees, for example)It is important to realize that if you are using a meter with temperature capability and a temperature measuring device with built-in converter you WILL NOT use the temperature function of the meter. You should use the millivolt range. (or whatever your device requires.) I suppose you might use an external converter with a meter with direct temperature measuring capability if the converter is for a probe that is not gepatible with the meter's built in converter. For example, if you had a type J thermocouple, you would need a type J external converter; you could not connect the type J probe directly to your temperature capable meter.
Final Thoughts:This is a confusing topic, and I will be re-writing this frequently. The main idea is that all Fluke meters can measure temperature with the right probe, or the right adaptor, and these aren't very expensive. Don't pay more to get this feature if you can accept using an external converter, or a probe with built in converter. The cost of a converter, or millivolt-output probe and meter may be less than the cost of a simple probe and "temperature reading" meter.

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