Amplified Sensors Explained

Amplified Quantum Sensor from Apogee Instruments
We offer an amplified version of our pyranometer and quantum sensor to allow for easy integration into systems that cannot measure small millivolt signals. There are two amplified options: 2.5 V and 5 V. The voltage listed is the maximum output at the maximum light for which the sensor is calibrated. It is also the minimum input voltage required to power the sensor. For example: the SP-215 has an output of 5 V when the solar radiation is at its maximum of 1250 W m-2. If the voltage supplied was only 4 V the maximum output would be 4 V, which means that the sensor would output the same for any light level over 1000 W m-2. This is something to watch for if you are supplying the voltage with batteries.

These sensors have been designed to have all the circuitry inside the head, the same as our non-amplified sensors. This means they are rugged and there is no worry about water damage to the circuit board. The circuitry is a basic non-inverting configuration of an operational amplifier (op-amp). The op-amp has been specifically chosen to have a low voltage offset and be physically small enough to fit inside of our current sensor body head. The op-amp has a max voltage specified at 5 V which is why the maximum output of our amplified sensors is 5 V. Included in the circuitry is a Zener diode that will short to ground if a voltage higher than 6 V is applied. This keeps the main circuitry from getting destroyed if the sensor is wired incorrectly.