Husdata datalogger for heat-pump

I got this husdata datalogger for my heat-pump.

It plugs in to a 3.5mm audio-connector inside the electronics box of the pump. On an IVT geo 312C pump it's fairly easy to install by removing the big front cover, then a smaller black cover, and then opening the electronics-box. I routed the wire into the pump via a tube-hole at the top, and then through the cable-hole of the electronics box (lower right). It plugs into a 3-wire 'BBT' interface.

The datalogger reads info from the pump and broadcasts it over wifi either to the husdata-website or over MQTT to any compatible device.

200MHz photodetector with OPA818, FGA01FC InGaAs photodiode, and RF=4k7

Here's another one-inch-photodetector using OPA818 with a 2pF@5V InGaAs fiber-coupled photodiode FGA01FC. With a transimpedance gain of 4k7 Ohms the bandwidth is just over 200 MHz. A TIASim model predicts the dark-noise and response reasonably well with a parasitic capacitance (over RF) adjusted to ca 0.12 pF. The spectrum-analyzer settings weren't ideal for looking at the dark-noise which should go down to the thermal-noise of the 4k7 resistor (dashed line) - but here the instrument noise-floor prevents us from seeing that.