Andrew Holman:

We’re about to start a day of testing. The first thing we want to do is make sure that the meter is set up correctly so that all the results we get are accurate. The Kyoritsu IR tester that we’re using, the first thing I notice is that the meter needle is not sitting at zero. So mechanically we’ve got to adjust that back. On the back of the scale, there’s a mirror that if we look directly over, we should only see one needle. If you can see the reflection of the needle, you’re getting what we call parallax error and you’re not lining it up exactly. So using a screwdriver to make sure we’re looking across the needle in that mirror so that we only see one. We slowly wind that down until we’re lined up on the mechanical zero.

Now that we’ve done that, we can start doing the electrical checks. So the first thing I’m going to do is switch down to battery check. We push the button to turn it on, and we see that the battery needle is within the battery okay range, so we’ve got plenty of battery in our meter. Next, we’re going to go up and we’re going to electrically zero. Now, because we’re using the low voltage resistance scale, we can actually turn the push button round to the lock position that will hold it for us. And all of a sudden, I see it jumping. So we’ve got a faulty red lead. There is obviously broken strands inside that cable, so that’s not going to be good to be used.

We’ll disconnect that lead and then I always tie a knot in it to indicate that that’s a faulty lead. We’ll now attach a new lead, turn the meter back on, and we see a much more steady reading. Even though it’s not zero, it’s a steady reading. So we’ve now got good leads. Now we use the electrical zero adjust. Once again, that parallax error to zero our meter. That’s the three ohm scale. If we’re going to use it at 500, before you take any measurements, always turn around and just readjust that electrical zero so that you’re there to go.

Now, we’re also going to use a trailing lead method, which means we’re going to have a long length of cable to get between the switchboard and inside the house, et cetera. So a reel of cable, we’re now going to connect in. And we notice, when we put that in the circuit, we’ve got the resistance of the cable. We’ve got to take that out. So once again, we can now adjust the meter down to zero to take into account that length of cable. So now when we run round, this is excluded from the measurement, and whatever we measure on the meter is going to be the resistance of the installation we’re testing. Always remember, when you stop using your trailing lead, it looks like it’s zero, but it’s actually gone down below. So we’ve now got to take that resistance back out and readjust up to recalibrate as zero on the meter.

So anytime we add or subtract that trailing lead, must go back and zero it out so that you get accurate readings. Now, the press to test and lock button is fine to use in the resistance scale, but once you switch up to insulation resistance, you are now going to be putting either 250, 500, or 1,000 volts on the end of your meter probes. It is definitely not a good idea to turn and lock that down. If you do, these become live, and if you forget, put them down and then pick up your meter, you’re going to get a very nasty surprise. So be very, very wary of using that lock in the insulation resistance mode. Now that we’re set up, we can now start the day and go and start to do some testing.