UTA-HOBO

The HOBO^® from Onset Computer Corporation is a miniature data logger that can be operate for months off a single lithium coin cell. We offer the UTA-HOBO, which is an amplifier that connects between LI-COR sensors and the HOBO, and allows the HOBO to log accurate light level data. The UTA-HOBO can take any of the LI-COR sensors as input (Pyranometer, Photometer, or Quantum PAR sensors, including the Spherical Quantum PAR sensor), and it provides a 0 to 2.5 volt full scale output compatible with the HOBO. The amplifier operates from the HOBO power supply, using the Onset "voltage input cable".

Left: A UTA/HOBO connected to a Li-Cor sensor on one side, and to the Onset HOBO data logger on the other side, via a "voltage input cable".

The UTA-HOBO differs significantly from our other UTA amplifiers. Modifications are made so that it can operate directly from the HOBO power supply, without affecting the HOBO battery life. The HOBO "voltage input cable" has three wires:

1. Common, reference point for the signal and the power.
2. Signal 0&endash;2.5 volts full scale.
3. +2.5 volt excitation power supply, comes on briefly only when the HOBO wakes up to take a reading, limited to 3 milliamps of current.

This excitation power supply is normally used to provide excitation to the thermistors that Onset sells for temperature measurement. Each thermistor draws about 125 microamps of current in order to make its measurement.

We use the 2.5 volts excitation to power the UTA-HOBO amplifier. The amplifier also draws only 125 microamps of current, the same as a thermistor. Thus, the UTA-HOBO will not compromise the battery life of the HOBO. The HOBO excitation voltage turns on only 2 milliseconds before the HOBO reads its first input channel. The UTA-HOBO responds fast, in well under one millisecond, fast enough to provide a stable and accurate light reading to the HOBO. Lastly, the UTA-HOBO amplifier has a rail-to-rail output, which means that, even when powered with only 2.5 volts, it can provide a full range output of 0 to 2.5 volts in response to input light signals.

The UTA-HOBO comes with special markings for the special 2.5 volts full scale output, and special instructions describing how to connect it to the HOBO and how to calculate the light levels from voltage readings shown by the Onset "Boxcar" software package. With respect to physical dimensions and layout, the UTA-HOBO is the same as the ordinary UTA amplifiers. It is available with either the gland nut or the BNC connector at the input.

• UTA/HOBO Documentation (Rev. D) - (192K PDF) - "special for HOBO" denoted on calibration label. Documentation to be used in addition to the UTA Rev. D Manual
• UTA/HOBO Documentation (Rev. C) - (320K PDF) - "special for HOBO" denoted on calibration label. Documentation to be used in addition to the UTA Manual