The Reference thermometers are high accuracy PT100 instruments that are supplied with a 5-point UKAS Certificate of Calibration. Each certificate indicates deviations from standards at various check points: -18, 0, 40, 70 and 100 °C. Special ranges may be certified by arrangement with the ETI UKAS calibration laboratory. The Reference thermometers are ideal for comparison checking the calibration and accuracy of other thermometers and probes, when used in conjunction with a stable temperature heat or chill source. The instruments measure temperature over the range of -199.99 to 199.99 °C with a resolution of 0.01 °C and an accuracy of ±0.05 °C. The units feature a simple on/off push button with open circuit ‘Err’ and low battery indication, when applicable. The Reference Plus thermometer incorporates the additional features of a max/min and hold function. The Reference thermometers are supplied with a permanently attached, high accuracy probe incorporating a 1/10th DIN PT100 sensor. The probe measures Ø3.3 x 130 mm and is supplied with a one metre PVC lead.