Frequently Asked Questions

Eliminating Interference from the Sensor

When installing the temperature sensor for the CTI-1/2 or TTT-1/2 in electrically noisy environments, some customers have been tempted to connect the third conductor (shield) labeled "Sensor G", "G" or "GND" to chassis or earth ground to help eliminate interference. Do not do this.

Connecting sensor "G" to ground on the CTI-1/2 or TTT-1 or TTI-2 will damage the device. The sensor is not ground referenced in these devices.

The TS-1 labeling is unintentionally misleading. The TS-1 sensor is used with several products and is, in fact, ground referenced in some of them. However, on the CTI and TTI series products the "G" connection is elevated above ground and should not be shorted.

There are a couple of options to suppress noise that do not interfere with the electrical signals of the temperature sensor:

• Use a cable with three insulated conductors plus shield rather than two plus shield. Choose foil shielded cable. Use the insulated conductors to connect the sensor signals. Connect the shield to chassis ground at the host device.
• If cable with two insulated conductors plus shield is already in use, bypass the shield to ground through a capacitor. This will allow the shield to pass AC noise to ground while leaving the DC voltage unchanged.

The bypass capacitor value depends on the frequency of the noise to be filtered. Good starting values are 0.1µF and 0.01µF, 50V or higher.