This is a reused project which previously used to be called the "Serial ADC". It was then a larger system which comprised an analog meter, with digital input, and an analog AC voltmeter in addition to this main unit. This turned out not to be very useful.
The present incarnation retains only the main unit, but adds an RF transmitter to it so that its measurements may be seen and recorded by either the Weather Loggeror the OLED Logger.
The Signal Conditioner was updated and refurbished and the main unit was provided with a new power supply and an added transmitter.
It has two components: The Signal Conditioner, and the Transmitter, interconnected by a ribbon cable.
1. Signal Conditioner.
This is very old; it dates to before single-chip microcontrollers were ivented.
It has eight Analog and four Digital inputs which it converts to a 0-4V DC range. One input is amplified, three have two ranges and one is differential.
Two of the Digital inputs are optically isolated: one AC and one DC. It also has 4 digital outputs. Two of the Digital outputs are optically isolated: one AC and one DC.
This Analog to Digital Converter is mounted on top of the Signal Conditioner, to which it is connected by a ribbon cable.
A Picaxe 40X2 micro-controller converts the analog inputs to 10-bit digital form and outputs these to the transmitter.
It is powered by a LiIon battery which has an attached charger, The battery is connected to a DC-DC converter in the Signal Conditioner which converts its output to regulated + and - 5V.
There is a second micro-controller which is powered via the on-off switch from the battery. It ensures that the battery is not over-discharged and cotrols the charginh current. It also shown the charge level via a rgb LED.