OP
No probs, at least you're aware there's a difference between analogue and digital testers (other than the way they actually display the results using a needle or digital display). That already puts you ahead of most of the pack.
The thing with testing in general is you usually want to take a measurement without actually having any effect on the circuit under test whilst you're doing it. If the instrument (tester) is connected into a circuit the instrument itself can actually alter the circuit characteristics which means just by connecting the tester you've altered the thing you want to measure. The difference the actual test instrument makes to the circuit is often called the 'burden'. Here's an article that explains some more.
Sometimes though to get an accurate test result you actually need to intentionally 'burden' the circuit to simulate a real-life event. With most of the 'safety' type tests such as touch voltage and leakage current tests we deliberately want to simulate the human body that would normally be in the circuit if leakage current was flowing. We often go to ridiculous lengths to make these human body simulations, often we add networks of resistors and capacitors to pretend there's an actual person in the test. Other times we cut up pieces of tin foil into scale models of human hands to simulate the area of contact that would be involved if a real person touched something and got a shock. Sounds pretty far fetched for middle aged men to be making tin foil hands but it happens quite regularly I can assure you.
Measuring touch voltage is definitely one of those tests where you'll get the most accurate or relevant result if you burden the circuit the same as a human body or person would burden the circuit if they were coming into contact with it. So....you'll get the most relevant result if the resistance across your test probes is the same as the the resistance (impedance actually) of the person who would be touching the same points in a real-life scenario.
TBH I'm going to come unstuck here again because I don't know which 'electrical models' the UK regs use for human body equivalents so anyone in the know feel free to chime in with info.
As an electrical engineer we use the UL medical electrical human equivalent models. Generally we consider the human body to look like this as an electrical circuit;
![[ElectriciansForums.net] Fido's Getting Shocked!!!](https://electricians.s3.eu-west-1.amazonaws.com/data/attachments/15/15536-b704ffb049a4032b00acfbd4cb949b15.jpg "[ElectriciansForums.net] Fido's Getting Shocked!!!")
Okay...let me know if I've lost anyone with the explanation so far, I'll probably finish off tomorrow evening.
The thing with testing in general is you usually want to take a measurement without actually having any effect on the circuit under test whilst you're doing it. If the instrument (tester) is connected into a circuit the instrument itself can actually alter the circuit characteristics which means just by connecting the tester you've altered the thing you want to measure. The difference the actual test instrument makes to the circuit is often called the 'burden'. Here's an article that explains some more.
Sometimes though to get an accurate test result you actually need to intentionally 'burden' the circuit to simulate a real-life event. With most of the 'safety' type tests such as touch voltage and leakage current tests we deliberately want to simulate the human body that would normally be in the circuit if leakage current was flowing. We often go to ridiculous lengths to make these human body simulations, often we add networks of resistors and capacitors to pretend there's an actual person in the test. Other times we cut up pieces of tin foil into scale models of human hands to simulate the area of contact that would be involved if a real person touched something and got a shock. Sounds pretty far fetched for middle aged men to be making tin foil hands but it happens quite regularly I can assure you.
Measuring touch voltage is definitely one of those tests where you'll get the most accurate or relevant result if you burden the circuit the same as a human body or person would burden the circuit if they were coming into contact with it. So....you'll get the most relevant result if the resistance across your test probes is the same as the the resistance (impedance actually) of the person who would be touching the same points in a real-life scenario.
TBH I'm going to come unstuck here again because I don't know which 'electrical models' the UK regs use for human body equivalents so anyone in the know feel free to chime in with info.
As an electrical engineer we use the UL medical electrical human equivalent models. Generally we consider the human body to look like this as an electrical circuit;
Okay...let me know if I've lost anyone with the explanation so far, I'll probably finish off tomorrow evening.
