Wiring for Chinese digital LED Tacho

[paulmo101]

Hi
I have just ordered a digital Tacho via Ebay for my lathe spindle and I have read that most of these seem to arrive with no wiring instructions for the sensor to the tacho readout and I was wondering if anyone on here has set one of these up?
The unit I have ordered is http://www.ebay.co.uk/itm/4-Digital-LED-Blue-Tachometer-RPM-Speed-Meter-Hall-Proximity-Switch-Sensor-NPN-/262842708255  and I have found a youtube video of someone fitting a SIMILAR unit to a fan 

&t=203s iresBUT this tacho only has 4 connections and 3 wires fitted which looks OK.  My unit ( in the photo on ebay) has a ribbon type cable with 5 wires coming out and the sensor has 3 wires.  I have found something on another video which suggests wiring PIN 1 on Tacho to power + and brown on the sensor.  PIN 2 on Tacho to power - and Blue on the sensor PINS 3 and 4 not used and PIN 5 on Tacho to Black ( I think signal wire) on the sensor.  Just wondering if that sounds OK and hopefully someone has used one of these and can confirm?
Thanks for reading

[John Rudd]

Ok, wired these before.....

Connect your supply ( 5 or 12v whatever is required.....) 1 is +, 2 is -, pin 3 is the sensor ground connection, pin 5 is the sensor signal wire.

The sensor wires are brown, black and blue.....

Black is the signal wire, connect to pin 5, the brown and blue wires connect to 1 and 3 respectively....

Hope it all goes wll for you....

[seadog]

Here's the diagram I got with mine.

[paulmo101]

Thanks for the replies -
John - The answer is great the only part i dont really understand is pin 3 Sensor ground  - sorry not sure what this means or where it would physically connect to any chance you can expand on that?
Seadog thanks for the drawing - I think thats the one in the ebay video - it only has 4 connections at the tacho end and I think mine will have 5 but most seems the same except signal wire to pin 5 instead of pin 4

Thanks again for the replies

[paulmo101]

Hi John - just reread (properly this time) and I now see that you say sensor ground BLUE goes to pin 3 on Tacho - thanks for that I will try that configuration when it arrives.  Confused me at first  as I read that blue sensor wire went to Pin2 and DC supply negative   Your wiring makes more sense.

Thanks again

[John Rudd]

So, is your  tacho up and running?