Operational Infrared Sensors Frequently Asked Questions

1. Operational

1. Can I run a TIR without power?

No. Aside from powering the ventilation system (and possibly heaters), power is required for the instrument itself. The thin film thermopile employed in the TIR-550 has higher output than many other thermopiles used in pyrgeometers and pyranometers, but it also has relatively high output impedance.

Incorporating a very low offset chopper-stabilized amplifier in the instrument with high quality resistors insures a low output impedance and high output voltage. This greatly reduces the burden on the data acquisition system employed. In effect, some of the errors normally associated with the data acquisition that are not counted in the instrument are already incorporated into the TIR-550.

2. Do I need to correct for the dome temperature of the TIR-550?

No. One of the design goals of the TIR-550 was to eliminate the need to correct measurements for dome temperature. The small size of the silicon dome and other design factors keeps the dome temperature very close to the temperature of the thermopile. Radiant heat exchange with the dome is proportional to (Tdome^4-Ttp^4); thus if the dome temperature tracks that of the thermopile the error is eliminated.