May be used as a portable instrument or bench top temperature calibrator for calibrating thermocouple and RTD temperature probes. It is small enough to use in the field, and accurate enough to use in the lab. The temperature is accurately controlled by Harts hybrid analog/digital controller. The controller uses a precision platinum RTD as a sensor and controls the well temperature with a solid state relay (triac) driven heater. The LED front panel continuously shows the current well temperature. The temperature may be easily set with the control buttons to any desired temperature within the specified range. The instruments multiple fault protection devices insure user and instrument safety and protection. The dry-well calibrator was designed for portability, low cost, and ease of operation. Through proper use the instrument will provide continued accurate calibration of temperature sensors and devices. Insert B (comparison block): 2 3/8,2 1/4, and 2 3/16 holes.