Well, most dissipative materials assosiated with ESD are mostly isolating materials like rubber or synthetic material. They have still high resistance like many megaohm. Using high Voltage to get an measurable currant is a good idea.

For common electric conductors as dissipative materiales usually measuring devices are the first choice.

My problem with your answer, Mr. Roth, is that many ESD safe materials are carbon-loaded or loaded with other DISSIPATIVE materials, and NOT insulators. To measure dissipative flooring or tabletops with 500 Volts would melt a pathway in the material. It becomes destructive. For insulators, yes, your answer makes some degree of sense, but ESD safe tables, floors, footwear, and chairs are not made insulatively. They designed specifically to direct excess voltages into a ground plane as safely as possible so as not to damage sensitive integrated circuits or to avoid a spark that could ignite an explosive or flammable material.

ESD means elektro static discharge.

You may remember the electrical shock as you opend your very first car on a cold winter day? In produktion it means to avoid the separation of the charge carrier. At 500V over a 1 giga-ohm resistor would result in an 5nA leakage currant. This is a quartert of 1mW.

I dont know your instrument but normaly they have a relative high internal resistance. If it is not directly conneted to the mains their is only limited power available.

In allowance of your instruments manual you may try to kill an 1/4W resistor with your expected amout of ohm and see what happens :-)

Save grounding and lightning conductors differs with "save against ESD". eg: High humidity in the air will already protect against ESD.

Eventough your instrument may intentionally not be buildt for measuring conductors, I woul be interested what is displayed if you trye to measure an 100ohm Resistor.

The calculation would say 5A.

But the Instrument would need 2500W for that. The resistor would be blown up!

I gues nothing happens and the Instrument says something like OV for Overload or maybe if it is realy good, it displays: 100 ohm :-)

If after this, the Resistor is still ok, you may trye to measure the currant with an further multi instrument to make shure not to damage your dissipative surface. Even though think of a suitable electrode contacting the surface for a proper result.

I know what ESD is. My company makes ESD testing and measurement products. Perhaps you misunderstand the application for which I am using the resistance meter. I am not using it for a power application, but to measure soft rubber with conductive or dissipative materials in it that can (even under small amounts of power) melt a trace, which would be the end of the usefulness of that material. The reason those materials melt is because they are not meant to carry current for long periods, even the duration in which a 500 volt meter can obtain an accurate measurement. My question is simply, why do the meters sold for this purpose have that kind of power at all? Even the specifications say not to use more than 100 volts, so why does the meter have that option? After all, you can get the same accuracy using 100 volts as you can using 500 volts, so why take the risk of providing that option on the meter?

Shane,

You keep calling 500V high power. Volts are not units of power, they are units of potential energy per electron or coulomb.

Power is expressed in units of watts, defined as voltage times current.

If a voltage source of 500V is connected to a 500 Mohm load such that 1 micro amp flows, the power delivered to the load will be 500 micro watts. 1/2 of a milliwatt is low power, not high power.

A meter designed for measuring high resistance needs to apply a high enough voltage to cause a measurable current to flow.

A properly designed meter has built in current limiting so that if the resistance being measured is relatively low, the applied voltage drops and the power delivered to that resistance remains low. As shown above, a current limit of ~1 micro amp would be an appropriate value.

Does the instrument have a spec for short circuit current?

If not, you could attach an ammeter to it and measure the current delivered to the low input resistance ammeter. At the same time, have a voltmeter reading the voltage across the ammeter.

Multiplying the voltage times the current would give you the power dissipated in the resistance being measured (in this case the ammeter).

You will find that the power delivered is well below the damage level for ESD control parts.

Mr. Hugel, your answer makes sense...if the meters in question were strictly current limited resistance meters. Unfortunately that is not always the case. I some situations, the tool involves current-sourced or voltage-sourced power supplies without a current-limiting resistor. In other words, there are situations where the user has to turn a knob to control the voltage. My question is simply: why is this occasionally sold as a tool for this purpose? If we know it can be dangerous, why not limit the ability of the tool? Is there some purpose that I am unaware of? Granted, some of these meters are older, but not all of them. Is this an example of newer designs imitating dated ideas without taking modern technology into account, or am I missing something?

For example, the Dr. Theidig Milli-TO-2 Resistance meter has a 500 V option that outputs 2 Watts of power. Not much, to be sure, but the assumption on the part of the manufacturer is that the user will always measure at 10 V and 100 V before ever using the 500 V setting. Still, since the meter was designed for items at less than 10^14 ohms, why even have a 500 V setting?

Shane, you are totally ignoring the basic concept of Ohms law, I=V/R as Ulrich Hugal above has already explained, the currents involved in the measurement are minute consequently the power generated is also minute P=VxI . Why are you having dificulty understanding this, like Ulrich has said the instrument will have short circuit protection built in.

Why would the Dr. Theidig Milli-TO-2 Resistance meter be designed to output a maximum of 2W?

That would be a question for the Marketing department ;-)

Why would it need a 500V output option to measure 10^14 ohms?

500V/10^14 ohms is 5 picoamps that the instrument must measure. Picoammeter design is not trivial.

"Picoammeter design is not trivial." is the best answer for what I am trying to solve for here. Thank you Mr. Hugel.

Most of the reason is well explained by others, and clearly quantified by Ulrich Hugel.

I would add that the measurement being made requires sufficient voltage for another reason as well, to make sure tiny insulating gaps or layers in the material being measured DO break down to avoid giving a false indication of high resistance isolation, which could lead to unexpected hazardous leakage when higher voltages are encountered in use.

That seems reasonable.

Most appliance testers and installation testers use 100-250-500-1000 VDC test voltages. But according to EN 61557 series at 500 V tester creates only 0,5 mA current. It should not harm anything.

But for a long period, ESD testers have been spesific testers with for instance 10-50-100 V insulation test voltages. With them specific DIN electrodes are used for instance point to point test to determine homogeneity of coating.

See for instance:

https://uk.rs-online.com/web/p/esd-test-meters/7768318/

HAve you even used an ESD tester on a benchtop or a floor? It will NOT damage the material. I don't know where you are getting that idea. Go test it.

Mr. Smith, I am more concerned about sheets of carbon-loaded plastic than typical ESD table mats and floor mats. Also I am partly asking because I want to know if a specific specification requires 500 volts. Since no one has answered me with a specific specification that calls out 500 volts, I have to assume there isn't one.

By the way, I would like to say that I appreciate all the answers from everyone on this topic, even though it hasn't solved the problem I am trying to deal with.

Have You checked standards IEC 61340-4-x and 61340-5-x for more detailed information?

Yes, I have 61340-5-1, and it doesn't explain why one would use 500 volts. 100 volts seems to be commonly used above 1x10^6 ohms, but otherwise not much guidance is really offered in the spec. Nowhere is 500 volts really mentioned. Other IEC specs I would have to buy. I have plenty of U.S. military specs and the ANSI/ESD spec of course.

Well, IEC 60364 part 6 includes 250, 500 and 1000 V insulation tests. But as You know, these concern only fixed installations. Maybe manufacturer's think testers like that could be more useful? Today I shortly tested one ESD - tester, it also had 10-100-1000 test voltages. I did not have time to read it's manual to figure out use of 1000 V.

Thank you, Mr. Lintula, your answer was most helpful.

But why would IEC and other specifications call out specifically 500V?

Why not 400V or 600V?

Let's see, my hand has 5 fingers. If I count all my fingers 10 times and multiply the two I get 500.

I suspect that we have here a manifestation of the human tendency to anthropomorphise material objects ;-)

Reijo Lintula : "But as You know, these concern only fixed installations."

How about a tester with a user set continuously variable output voltage, and/or a variable current limit?

It could be a premium product for 'power users'. (no pun intended)

Shane, do you need a custom instrument? What kind of specs for voltage, current limit or maximum power sourced do you need?

How big do you think the market would be?

Alternatively, you could build your own setup with a variable voltage and current limit HV supply and a picoammeter. Possibly automate it with LabView.

Well it was for one customer, so the volume was low to say the least. The sale never went through, or at least not yet, and I wasn't the one directly involved. I have more or less been assigned with post-mortem work. But you are right, we ended up trying a solution using a current source and measuring the resultant voltage to see what the resistance of the material was. It turned out to be the wrong tool for the job, and we melted a couple of samples by turning the knob a little too quickly. Unfortunately I have to chalk this up to a "learning experience." That probably means that failure has taught me more than I wish it did. I sort of threw myself into it headlong without a plan, and that was something I never like to do.

What kind of HV compliant current source was it?

In what sense was it the wrong tool for the job?

It was the wrong tool because the probe itself physically destroyed the samples. They were thin pieces of material loaded with carbon, and before we received them, we were under the impression that they were durable sheets of rubber-like material. They shredded when they came into contact with the probe. I thought it was a weird decision to use the probe. It was built to be compliant with ASTM D-991, and it has metal ridges where rubberized material would normally be gripped. With this material, it was just too thin, and it was cut or torn by the probe. The We make a perfectly good ESD S11.11 probe that would have worked with an ordinary 10 volt meter. My fear (or paranoia) at the time was that we would melt this thin material. Using low current sources, it would have been fine, but we were not careful with it, so we ended up seeing a sample briefly emit a small puff of smoke and suddenly change its electrical characteristics. Sort of embarrassing, really. Furthermore, every ESD spec tells you not to wait too long (usually only 15 seconds), because the longer you wait, the higher the resistance is in some carbon-loaded materials. You see, even at low power, carbon-loaded materials have a tendency to "burn a trace" over time, which permanently changes their electrical properties. That's why I had the concern about this in the first place. The resistance will seem to rise until it reaches a peak and then it can drop precipitously. This is especially true for Resistivity below 1x10^3 ohms per square.

It seems there are many things being talked about here, and the solution is to get a tester which is designed to test the article you wish to test. If there is not a dedicated tester, it is up to the engineer to design the circuit. The elements of the circuit are a Thevennin source (voltage source followed by series high resistance), a gate to limit exposure time as required, and a sensitive voltmeter across the load device under test or current measurement device in series. As there is a high series resistance, voltage can be easily converted into device under test resistance. It is up to the test engineer to understand the device being tested and choose parameters accordingly. There is a fairly

broad range covered by the Fluke 1587 insulation resistance tester, and there are testers used to verify wriststraps and static mats in another category where leakage is a desirable quantity, but again, you must understand what you are testing or buy a tester designed for the device.