80L82

I've done all the items to repair my tach and now have it working. However, the mechanic that put the circuit board in did not zero it out. I'm wondering if I can zero it out without taking it out. I have the 12volt needed from the car. Can I take off the lens and zero the needle in the car?

thanks in advance!

hunt4cleanair

Not exactly. You need a tach meter and calibrate the tach with the tach meter reading. However. this depends on the tach board and whether it has a pot that can be calibrated. Some. like Wilcox (he is a vendor here but markets his board to other suppliers) has an adjustment screw (think its blue). Others come pre-calibrated.

Search the Willcox website for tach calibration and see what you find. Others may be able to provide more specifics...but don't be moving needles around until you understand what you're doing...my suggestion!

80L82

I bought one that was described as pre-calibrated. According to Wilcox's video you zero it with the needle?

'75

Pull the clear face off, pull the needle off the tach, turn on the key and put the needle on at zero.

80L82

Thanks!

Datacat

These electronic tachometer kits come pre-calibrated, but if you want to check it or suspect the supplied calibration is not accurate enough, you need a signal generator that can supply at least about 8 to10 volts. (The CAL output of an oscilloscope will not do, as they are usually limited to about 2 volts.) With power supplied to the tach, you put the needle on the tach pointing to zero and then use the signal generator and the calibration screw on the electronic module, which you cannot get to unless you pull the dash out of the car.

I have used this $67 signal generator: "KKmoon High Precision Digital DDS Dual-Channel Signal Source Generator Arbitrary Waveform Frequency Meter 200MSa/s 25MHz"
That signal generator works, but it requires a lot of confusing button-pushing to get the waveform you want. It is very useful to have an oscilloscope on the output to double-check you got what you wanted.

A great automotive oscilloscope is the $139 Picoscope 2204a.
This is a small 2-channel digital oscilloscope that plugs into your computer for the display. Software is free for both PC and Macintosh computers. It runs great with a battery-powered laptop computer; the KKmoon signal generator needs to be plugged in to AC wall power.

The electronic tachometer is insensitive to the details of the waveform, so almost all you really need is to get the frequency right. I varied the duty cycle of a square wave from 10% to 90%, with no variation in tach reading.

Thomas Schacher

Twenty seven

Datacat

I have no idea what that is suppose to mean.

Thomas Schacher

Sorry about that data cat. That was an answer for a different feed that I sent too late at night.