Let’s start anyhow by discussing what I mean with a “temperature dry block” in the article.

A temperature dry block is sometimes also called a dry-well or a temperature calibrator.

It is a device that can be heated and/or cooled to different temperature values, and as the name hints, it is used dry, without any liquids.

A dry block typically has a removable insert (or sleeve) that has suitable holes/borings for inserting temperature sensors into.

The dry block typically has its own internal measurement for the temperature, or you may use an external reference temperature sensor that you will insert into one of the holes.

Commonly a dry block has interchangeable inserts, so you may have several inserts, each being drilled with different holes, to suit for calibration of different sized temperature sensors.

It is very important in a dry block that the hole for the temperature sensor is sufficiently tight to enable low thermal resistance between the sensor and the insert. In too loose of a boring, the sensor stabilizes slowly or may not reach the temperature of the insert at all due to stem conduction.

Commonly, you would insert a temperature sensor in the dry block to be calibrated or calibrate a temperature loop where the temperature sensor is the first component in the loop.

The main benefits of a dry block are that it is easy to carry out in the field and there is no hot fluid that would spill when you carry it around. Also, a dry block will not contaminate the temperate sensors being calibrated.

Dry blocks are almost always used dry. In some very rare cases you may use some heat transfer fluids or pastes. In most cases you may damage the dry block if you use liquids.

Using oil or pastes also cause a potential health and fire risk if later used in temperatures higher than for example a flash point of the foreign substance. A 660 °C dry block that has silicon oil absorbed into its insulation may look neat outside, but it will blow out a noxious fumes when heated up. Calibration labs everywhere are probably more familiar with this than they would like to be…

As drawbacks for dry blocks, we could consider lower accuracy/stability than with a liquid bath and more difficult to calibrate very short and odd shaped sensors.