Universal Transconductance Amplifier


The UTA is a special purpose amplifier that converts the microamp-level current output of LI-COR light sensors to a corresponding signal voltage. The UTA provides a simple interface between LI-COR sensors and voltage input data loggers, chart recorders, HVAC, and greenhouse control systems.

Will the UTA work with LI-COR's new "R" version light level sensors? Yes. Please follow the correct wiring diagram as it has changed.

The UTA can be configured at EME Systems, or by the end user, for any one of a large number of gain settings through manipulation of two switch blocks. The calibration tag provided by LI-COR with each sensor, in conjunction with the preset amplifier gain factor, can be used to compute the light levels incident on the sensor with a high degree of accuracy. Alternate gain settings are available on special order. One of the most popular alternate settings is a 2.5V output for use with Onset HOBO data loggers.

The Rev. B version of the UTA includes a bias generator that allows the output to swing closer to ground.

On the UTA shown in the photo, the input cable from the sensor will enter through the gland nut to the left and the output cable to the equipment will exit through the gland nut on the right. The UTA is also available with a BNC connector on the input*. The calibration label on the outside of the enclosure is marked with the applicable gain setting. Wiring instructions and calibration notes are included with each UTA.

* Some customers have ordered the UTA without a BNC connector even though they have a "sa" model LI-COR that has a BNC connector interface. They have done this either on purpose, because they want to take advantage of the waterproof nature of the gland nuts (as seen in the picture above), or they have done it by mistake. In either case, the BNC connector can be cut off of the LI-COR sensor and thus a "sa" model LI-COR sensor can be turned into a "sz" model LI-COR sensor. If you would like to make this conversion, download the PDF instructions on how to remove the BNC connector from a LI-COR sensor.