A current sensor doesn't really care about the voltage, it works at a constant current, with the only limitation being the power supply rails.
So you must load the output to ensure it always stays beyond max voltage at the highest output, or the current won't be able to flow.
This circuit uses 147ohm load, so the voltage will be 17.64V (120mA) and 8.82V(60mA), which I don't think it'll be a problem for the sensor (yet to know the model).
Using a darlington configuration, you can turn on a relay with microamps at the base, so you only need a small capacitor to store the energy from the peak detector.
Adjust the potentiometer to set the threshold, I simulated 45% to trigger at 70ma.
Instead the 2N2222A, use a BC547C, has much greater gain (400-800 vs 75-300).
It doesn't care if using AC or DC, since the peak detector is also a half wave rectifier.
I've tested it at 1Hz, holds the relay switched on with max 0.9Vce.
In an industrial setting I would use a PLC with analog input.
Do industrial PLCs work with such current ranges? I only know 0-20 and 4-20mA sensors!
Is the current AC at 60mA DC or AC untriggered?
Any how this should work. Runs on 6 to 40V DC- under £5 to make. (Attachment Link)
Terry, 24V relays usually have a fairly high coil impedance, around 1Kohm (we're talking about a simple relay, not a huge 1000amp contactor).
Simple math shows that it would only require 24mA (actually, the switching threshold is always lower than the nominal current).
So the relay will be always turned on in that circuit. In any case, you have no control over it.