Introduction

The PAR-sensor measures the section of the light spectrum that converts the plant into growth (photosynthesis). PAR stands for Photosynthetic Active Radiation, and includes the light spectrum between 400 and 700 nm. 

The figure above shows the LI-190R response and the ideal quantum response in photon units	The figure above shows the LI-190R response and the ideal quantum response in energy units

The PAR sensor can be mounted outside or inside the greenhouse. When mounted inside the greenhouse, the sensor can be mounted above or below the grow lights, depending on how it is to be integrated with the lighting control. 

Connecting the PAR sensor

1. Connect the LI-COR PAR sensor to the UTA amplifier input.
   • Pass the LI-COR sensor cable through the UTA cable gland nearest the 2-terminal (blue/black & brown/light green) connection block. Loosen the gland nut if necessary.
   • Connect the  LI-190R PAR sensor signal wire (brown) to brown/light green terminal in the amplifier
   • Connect both the LI-190R signal return wire (blue) and shield to blue/black terminal in the amplifier.
2. Connect the UTA amplifier to the Compass.
   • The black common wire from the UTA needs to be connected to the field ground of the input as well as the 0 VDC of the DC power supply. These should have been connected in the Compass panel during production but make sure no one disconnected it. If a UI8 module was added, make sure that the UI8 field ground is also connected to the field ground terminals in the panel.
   • The red power wire from the UTA needs to be connected to the 24VDC power supply reserved for field devices.
   • The green signal output wire needs to be connected to the corresponding universal input.
   • 

Setting PAR sensor calibration values in Compass

Each PAR sensor is supplied with a calibration certificate.  This calibration certificate is needed to calibrate the sensor in the Priva Compass. If you cannot find your certificate, you can go to Licor's website and download it.  The PAR sensor needs to be cleaned every three months and recalibrated every 2 years after field deployment.

Each PAR sensor is also supplied with a UTA (Universal Transconductance Amplifier)  since the signal from the sensor itself is too low to be measured by the Compass. The amplification of the UTA can be determined on the label on the side of the UTA

Calibrating the PAR sensor

Using the calibration value from the certificate, use the table below to determine the proper multiplication factor. The multiplication factor is dependent on the model of amplifier.

The type of amplifier can be determined based on the label on the side of the amplifier.

Calibration value
125 umol/s/m2 per microamp	73	104
126 umol/s/m2 per microamp	72	103
127 umol/s/m2 per microamp	72	103
128 umol/s/m2 per microamp	71	102
129 umol/s/m2 per microamp	71	101
130 umol/s/m2 per microamp	70	100
131 umol/s/m2 per microamp	70	99
132 umol/s/m2 per microamp	69	99
133 umol/s/m2 per microamp	69	98
134 umol/s/m2 per microamp	68	97
135 umol/s/m2 per microamp	68	96
136 umol/s/m2 per microamp	67	96
137 umol/s/m2 per microamp	67	95
138 umol/s/m2 per microamp	66	94
139 umol/s/m2 per microamp	66	94
140 umol/s/m2 per microamp	65	93
141 umol/s/m2 per microamp	65	92
142 umol/s/m2 per microamp	64	92
143 umol/s/m2 per microamp	64	91
144 umol/s/m2 per microamp	63	90
145 umol/s/m2 per microamp	63	90
146 umol/s/m2 per microamp	62	89
147 umol/s/m2 per microamp	62	89
148 umol/s/m2 per microamp	61	88
149 umol/s/m2 per microamp	61	87
150 umol/s/m2 per microamp	61	87
151 umol/s/m2 per microamp	60	86
152 umol/s/m2 per microamp	60	86
153 umol/s/m2 per microamp	60	85
154 umol/s/m2 per microamp	59	85
155 umol/s/m2 per microamp	59	84
156 umol/s/m2 per microamp	58	83
157 umol/s/m2 per microamp	58	83
158 umol/s/m2 per microamp	58	83
159 umol/s/m2 per microamp	57	82
160 umol/s/m2 per microamp	57	81
161 umol/s/m2 per microamp	57	81
162 umol/s/m2 per microamp	56	80
163 umol/s/m2 per microamp	56	80
164 umol/s/m2 per microamp	56	79

It is possible that the PAR sensor measures a small amount of light (less than 4 µmol/s¹ m²) at night. This can be corrected by entering an offset in the ‘ light sensor zero calibration offset’ found in the configuration menu.

Specifications

LI-190R Specifications

Universal Transconductance Amplifier Specifications

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