# Optical pulse sensor or CT clamp for Solar PV monitoring **URL:** \ **Category:** Hardware\ **Created:** [4 September 2021 14:43 UTC](https://community.openenergymonitor.org/t/optical-pulse-sensor-or-ct-clamp-for-solar-pv-monitoring/18535 "2021-09-04T14:43:31Z")\ **Posts on this page:** 1\ **Showing post:** 4
**Author:** ![Robert.Wall](https://community.openenergymonitor.org/user_avatar/community.openenergymonitor.org/robert.wall/32/38246_2.png) [@Robert.Wall](https://community.openenergymonitor.org/u/Robert.Wall)\ **Post date:** [4 September 2021 23:12 UTC](https://community.openenergymonitor.org/t/optical-pulse-sensor-or-ct-clamp-for-solar-pv-monitoring/18535/4 "2021-09-04T23:12:57Z")
> [@Stephen2](#): > > I was not going to purchase any optical sensors. > Since i have found little infor regarding them on the Community. Really? Have you looked at the links on the Shop page? What “infor” do you need that isn’t on that page or linked from it? Or maybe you didn’t find these topics > [@First try with EmonPi - Pulsecount stuck at 1](https://community.openenergymonitor.org/t/first-try-with-emonpi-pulsecount-stuck-at-1/7375/16): > > Some measurements: I used a white LED reading lamp, with several layers of draughting film over the front to attenuate the light. The sensor was therefore looking at a bright but diffuse patch of light approx. 30 mm in diameter. EmonTx V3.4 Condition Output voltage Distance to light source Just detecting logic '1' 1.42 V 570 mm LED just visible 3.28 V 460 mm LED bright 3.28 V 400 mm EmonPi Condition Output voltage Distance to light source Just detecting logic '1' 1.35 V 710 … > [@Adjusting sensitivity of Optical Pulse Sensor](https://community.openenergymonitor.org/t/adjusting-sensitivity-of-optical-pulse-sensor/8399/21): > > Further investigations with Optical Pulse Sensor connected to emonTH. No external pull-up or pull down resistor connected for these measurements, but a 0.1 uF capacitor left connected between IRQ and Gnd. Vcc = 3.346 V Virq with sensor in darkness = 0.745 V Virq with sensor illuminated = 3.333 V BUT the LED on the sensor can be misleading ie in partial illumination Virq varies with light level but the sensor LED remains off. In partial illumination Virq can be as high as 3.330 V (ie high) and … > [@Stephen2](#): > > As the old geo Chorus used 2 of them. Is something missing from that sentence? --- _[View the full topic](https://community.openenergymonitor.org/t/optical-pulse-sensor-or-ct-clamp-for-solar-pv-monitoring/18535)._