Cheap Multi Functional Tester

I got one of these a few months ago and have ended up buying half a dozen as xmas pressies

They can go right down to non contact low voltages from mains supplies and can do very low voltage/current stuff via direct contact, both ac and dc

So handy for the house, and on a car, for under a fiver from various outlets

They seem to detect EM energy but at very low levels can do contact work

Anyway, thought I'd share, someone else may find one handy

(EDIT They seem to do under 12v no problem, despite what the blurb says)

**LINK**

Edited By Ady1 on 14/12/2017 10:29:21

Emergency stop press !

It doesn't seem to work in cars (dang!)

It only detects low DC stuff which originates from a mains supply

the blade  is connected to the base of a NPN darlington transistor via a resistor of several meg ohms

to light the LED the screw driver blade has to be a volt or so more positive than the end cap/ battery negative terminal

if you touch the chassis with one hand and the tester/ screwdrivers battery cap with the other hand

the LED does light when the blade is in contact with a +12V DC connection

John

PS

diagram

Edited By john swift 1 on 14/12/2017 14:04:44

I don't think this can truthfully be described as a Tester, it only indicates and should not be relied upon 100% when using on any mains circuit. Similar to the modern Litestick unit which indicate mains voltage.

Emgee

Aha! thanks gents

So contact work only on a car etc

So contact work only on a car etc

There are lots of cheap multimeters suitable for use on cars - most of which I would likely avoid, mind.

Might be useful elsewhere, I suppose...

I have an interesting one with an LCD display that picks up live mains without contact.

I wouldn't bet my life on it but it is useful for fault tracing.

Neil

You want to get one of these volt stick things. Available from various suppliers and are great for sanity checking that mains wiring is safely turned off before licking the bare wires. Obviously you need to check it registers against a "known live" wire too. There is no absolutely safe tester that is proof against broken probe / wire / circuit etc, so this can only provide an extra level of indication. They have a green and red LED and they beep when turning on and off (including when they autosleep).

Murray

Something I've not quite managed to justify (even to myself!) would be one of these signal tracers. The transmitter injects a signal into the mains circuit and the (non-contact) receiver sniffs for it near the circuit breakers.

Edited By Muzzer on 14/12/2017 16:18:10

When there are alternatives I can’t see the attraction in buying a tester that relies on bodily contact to work. A decent little multimeter from Rapid Electronics will only cost a fiver or so and is probably more versatile.

Best story I heard about these was somebody loaned theirs to the apprentice who managed to drop it in a bucket of water. After drying the outside he returned it. Next time the owner used it he got a bit of a wallop.

Mike

.

In the early 1970s, I worked briefly for a TV Rental Company, where the engineers carried the neon-only version of these testers.

A favourite trick was to replace the dropper resistor with a fuse

With mates like that ...

MichaelG

Exactly if that resistor goes short circuit you will be pluged into the mains, the electrians I worked with would never use them

I've rarely, if ever, come across a normal carbon type resistor go Short Circuit, only go High Resistance, or Open Circuit.

Capacitors on the other hand...........

Regarding the little beepy flashy pen mains detectors, I've never been comfortable with them to detect the absence of mains, just the presence of a voltage. It's always hard to prove a negative.

The way I sometimes use one is to clip or place it next to the circuit to be tested, such that it is bleeping/flashing permanently. Then when you turn off the switch and the detector notices, you know you've isolated the correct circuit; assuming that it's not dual fed of course.

Also, even with a meter, test the tester before testing the circuit, to help prevent false readings.

Bill

I have had one of those for many years and have never trusted it to indicate voltage of any magnitude. However, it is excellent for indicating continuity or otherwise. Checking fuses before dismantling an appliance is just an example. It's other advertised uses have to be given the caution it deserves! A fiver for your life..?

trev

Good quality test equipment for isolation testing is unfortunately expensive. It should include a proving unit to test the tester after making the checks for isolation. This goes some way to check against equipment failure. I must say that I prefer something like a Martindale tester to the types with a row of LEDs. I know some of them meet all the standards for testing but I like it to be as simple as possible.

Mike