Modifying a multimeter with added MOVs or a spark gap does not make it safer, not necessarily. The design of the circuit board, the placement of the components, and the actual values are to be taken as a whole. It is possible that the current limiting resistors on the input jacks are not up to the task and putting an MOV in there is just adding a miniature bomb ready to go off if the current goes through it. I sincerely think that they aren't there as a cost cutting measure, but they could have been omitted to prevent a bigger problem that wasn't anticipated in the original design.
Labeling a meter with a specific safety rating incorrectly is wrong and no one can defend that. What is the harm? Well how about the person who is buying his first meter and watches some youtube video about meter ratings and sees that the UT71E is rated for CATIV 600V and then proceeds to use it on the meter connection to his house and gets seriously burned? This is not a problem? Sure the meter might be good value for the money, but only if you know that the ratings are a lie and know what you are buying.
No one can argue that meter with exactly the same specs is not a better meter if it has the correct CAT rating on it instead of a bogus one. No one can argue that a meter with a bogus rating is being sold truthfully. No one can argue that everyone has the time to take apart every meter on the market before they buy one and have them all tested individually for safety. That is what the standards are supposed to be for and why people die and get burned when they trust the CAT rating on a meter stuck on there by greedy assholes, culturally related or not. Thanks to off brand thieves and liars, people die. It is that simple.
That is why I started the thread about meters that don't appear to meet their CAT ratings, so that there was a reference and some guides for people to check. I have not updated it for a long time but it seems it needs to be again. How a sticky that is there for all to read with warnings about Uni-T meters has been missed, including by Dave, I don't know.
So Uni-T makes some shit meters, and some blatantly unsafe ones. DON"T BUY THEM. If they make safer ones, them buy them and send them a message that people don't want the bad ones. Unfortunately education and culture do play a part in this and where I live quality seems to be a joke and to ask for service is an insult. Mastech, Victor, Vichy, etc, all have deservedly bad reputations but then you get people here and other forums complaining about meter snobs who don't understand the needs of the less fortunate who don't have the money. Again what is the point of these discussions? EDUCATION. The poor and underprivileged need the same education so at least when the buy junk, they know, and they know the risks and limitations.
I have yet to see a Mastech I would recommend, nor a Vichy, most Digiteks no, and if I do recommend anything for anyone from the really budget class I make it a point to educate that the bogus CAT ratings are a joke and they should keep the probes out of the wall socket. Yes, not everyone has $100 to spend on a meter, some not even $50. This is exactly who needs to know what they are buying and why they need to be careful where they use it.
As far as the UT61E I had. It fried at 2500VDC. This was above the rated input but not above the impulse it is supposed to protect the user from. Maybe around 10mA passed through from the test and it caused nice sparks to jump around the selector dial. If it had been a 500A pulse the meter probably would have exploded. If you can see the spark at <10mA image the arc at 500A!!!
Again, say what you want about a meter having "value" even if it doesn't meet its safety rating. Go tell that to the people's friends and family who died in the story linked to earlier.
<Edited for grammar and spelling>