Temperature calibrators are capable of measuring or simulating temperature curves associated with RTD and Thermocouple devices. A good T/C calibrator will quickly adjust for the difference in temperature between your I/E workshop and the plant to ensure it's cold junction sensor is at the same temperature as your instrument. In the case of RTD calibrators, if you are using 'Smart' instruments, make sure the calibrator you select will work with the pulsed excitation currents put out by your DCS system for these devices.
In order to calibrate sensors a heat bath or dry well tester is needed. Are the sensors you use short or have a large diameter? Do you primarily use thermocouples or RTD's? Call us for information on the one that is best suited to your budget and needs.