Applies To: readouts: 1502A, 1504, 1523, 1524, 1560, 1529
These readouts use a four-wire resistance measurement circuit. The potential sensing leads feed into the input of a very high impedance amplifier. When there is no probe connected the high-impedance inputs are left floating and the amplifier becomes sensitive to spurious bias currents and electromagnetic interference.
When a probe is connected, it provides a low impedance path for any spurious signals so they do not reach the amplifier and produce measurement error or noise. The product is designed and tested to meet worldwide EMC (Electromagnetic Compatibility) standards and published accuracy specifications in a wide range of environments when connected to a temperature sensor.