Bench multimeter calls for ground (which I do not have)

[xlzslayer]

I recently treated myself to a Fluke 8808A, I wasn't going to, I was going to get a cheaper handheld meter, but I couldn't resist the deal I found right before I was going to purchase the handheld meter.

The meter isn't here yet, I actually purchased it from abroad (USA) and have a family member that will be bringing it with them soon. As the responsible person I am, I checked the manual, figured out I'll need to change the line fuse since we use 220v here, but was also met with a big warning in bold text:

To avoid shock hazard, connect the factory supplied three conductor line power cord to a properly grounded power outlet. Do not use a two-conductor adapter or extension cord, as this will break the protective ground connection. If a two-conductor power cord must be used, a protective grounding wire must be connected between the ground terminal and earth ground before connecting the power cord or operating the Meter.

I live in Lebanon, we only really have 2 prong outlets in apartments and houses, I believe the grounding is done externally. How big of an issue will it be to plug the meter straight into a 2 prong outlet? If it is an issue, can I do something about it?

[bdunham7]

You'll need to pop the fuse holder out and then the voltage selector block and flip that around to the 240 setting, but if you don't have the MDL 1/16 fuse by then you can run it for a while with the MDL 1/8 as that will blow and prevent any fires.  The ground issue can be handled with a separate ground wire from a grounding rod or plumbing to the small ground screw on the back of the unit.  The center pin of the input plug is connected directly to the chassis, so I wouldn't ignore the grounding issue.  If you have only two-prong plugs on your cord but IEC C13 plugs on the other end, what do those look like?  Power cords like that here exist, but they don't have any hole in the center so you cannot plug them into 3-pin equipment sockets. 

Edit: If you are going to have trouble getting the exact MDL 1/16 fuse and if there is still sometime, you might want to order some now and have them brought with the meter.  They're 3AG-sized (6 x 32mm) and you shouldn't substitute anything else for MDL.

[xlzslayer]

I'll be trying to get the exact fuse replacement required, but it'll be quite a bit later (a month or so). I didn't realize that fluke listed the exact part number for the fuse until recently, and said family member will be coming today-tomorrow for a few days and will be leaving again for a month or so. I can run the meter on a 120v transformer in the meantime, will that suffice temporarily?

We use an EU variant of the C13 that allows you to connect 3-pin equipment sockets into 2-prong outlets (check attached image). The grounding issue will be a bit difficult to fix, I live in an apartment and we use PVC pipes (or some other kind of plastic) for our water supply. I don't really have access to a grounding rod, nor do I have a place to plant one in the ground. Not having a dedicated ground hasn't been much of an issue for other appliances, just little zaps here and there, but the meter is a different type of instrument so it got me a bit worried after seeing that warning.

[JustMeHere]

Open your service panel and look for a ground.

Also, and I'm no expert, but GFCI could be useful here.  My old house had no ground wires (except bathroom) but had a GFCI panel.  It passed inspection. 

The bathroom had to have a ground and it's own local GFCi for code.  I had that rewired.

Notre the service panel was grounded although most of the house wasn't......

Also, are the receptacles in the bathroom grounded? 

[Doctorandus_P]

The most important thing will be the voltage selection. In the US a lot of 120V stuff is used, so verify and fix that voltage setting when you get your DMM.

As for the protective earth. It's sort of important, and a bit more so when working with electronics. It's also important for PC's.

Here in the EU, mains voltage sockets both with and without protective earth are used. In my living room where I wanted to use my PC and my electronics workbench, there was no PE, so I pulled the GND and phase wires out of the tubing, added an earth wire, and then put them all 3 back in the pipe, and I changed the wall sockets. In the metering cabinet there is usually a connection for PE.

If you don't have PE on a regular PC, then you may feel a tingling feeling when you touch it. This is because there are filter capacitors connected between PE and both live wires (or Live and GND). As a result, PE (and the whole outer case of the PC) has half of the mains voltage when the PE wire is not connected externally.

I'm not familiar with electrical installations in Lebanon, but I guess it's not the most developed country. If you don't have a PE connection in your house at all, you can make your own. You can make it from a copper water pipe of a few meters long, and then drive it vertically into the GND (of course depending on local GND conditions).

There are different ways of getting such a pipe in the ground, one way is to connect it to a pump, and then force a lot of water throught the pipe. The water will wash away the soil at the end of the pipe, so you can sink it slowly into the ground. Another way is to make (buy?) an adapter for a hammer drill, and then use the hammer drill to push the pipe into the ground. First dig a shallow pit, so you can connect the PE wire to the pipe under the ground, and you can cover it up without anything visible above ground. You can search youtube for video's about the details.

In the old days PE was sometimes connected to the water distribution network, but as plastic water pipes have become more common over the last 50 years, this is now deprecated where I live.

[ejeffrey]

Open your service panel and look for a ground.

That's not super useful if the OP lives in an apartment and the service panel is not near where they will use the meter.

Also, and I'm no expert, but GFCI could be useful here.  My old house had no ground wires (except bathroom) but had a GFCI panel.  It passed inspection. 

GFCI alone isn't really ideal for test equipment like this.  GFCI will shut off the power to the instrument if the instrument itself develops a ground fault.  However with test equipment the concern is that you might connect energized equipment to the meter.  GFCI on the meter circuit can't protect against that.  So it's definitely better if you can find an actual ground somewhere. 

[bdunham7]

I'll be trying to get the exact fuse replacement required, but it'll be quite a bit later (a month or so). I didn't realize that fluke listed the exact part number for the fuse until recently, and said family member will be coming today-tomorrow for a few days and will be leaving again for a month or so. I can run the meter on a 120v transformer in the meantime, will that suffice temporarily?

You don't need to get a Fluke-specific fuse (p/n 163030), but you do want the MDL 1/16.  These are commonly available here and the eBay ones typically aren't fake. Sure, a transformer will work, if it is an isolating transformer that's even better.

We use an EU variant of the C13 that allows you to connect 3-pin equipment sockets into 2-prong outlets (check attached image). The grounding issue will be a bit difficult to fix, I live in an apartment and we use PVC pipes (or some other kind of plastic) for our water supply. I don't really have access to a grounding rod, nor do I have a place to plant one in the ground. Not having a dedicated ground hasn't been much of an issue for other appliances, just little zaps here and there, but the meter is a different type of instrument so it got me a bit worried after seeing that warning.

The meter is no more or less hazardous than other appliances and instruments that should be grounded.  The front panel inputs are all guarded (isolated) from ground or power and the only way the chassis would be energized is if there were a failure of the internal primary wiring (power switch and inlet) or transformer.  Without a ground the chassis could float up to some voltage or could have AC leakage current energize it to some potential but without much current.  This might cause increased residual counts in the AC ranges or give you a slight buzz if you handle the meter. 

[pqass]

Given these pictures of the insides, I don't think there is much shock risk with an unconnected ground because:
a. the front panel is all plastic with rubber buttons
b. the input jacks are floating (all meters in this class have floating inputs)
c. use of a quality, galvanically isolated transformer power supply

The notice is CYA (cover yer ass).

The only remote danger I see is that the transformer primary windings shorting to the core; energizing the case.

If you're concerned,
a. don't touch the painted metal case while plugged-in
b. use an insulated pad under your feet
c. use on a non-metallic bench.
d. wrap metal case with insulated sheet (allowing for air exchange)

Disclaimer: use at own risk.

Haters: you may now begin to tell me I'm very wrong.

[TimFox]

Assuming the power entry connection employs a standard three-terminal line filter:
Whatever the case of the filter (connected to the third prong that is not connected with a two-prong outlet) is connected to will see an AC voltage equal to half your single-phase voltage (120 V for your 240 V feed) in series with a medium capacitance from the filter.  With some equipment, that might be metal that you can touch.  If the Fluke carefully insulates everything you can touch from that connection (e.g. BNC shells), then you are safe, unless that insulation should fail.  The design of these filters limits the capacitance to ground to keep the current to a non-lethal value, but it can be a noticeable jolt.  At work, we named that jolt the “Dan effect”, as in “It’s hard to shock Dan, but…” after he encountered an ungrounded Diesel generator at a foreign construction site connected to a grounded system.

[bdunham7]

Assuming the power entry connection employs a standard three-terminal line filter:

This meter actually doesn't,  AFAIK (unless it is well hidden) and it just has a inlet/switch/fuse/voltage selector block all combined in one unit.  No need for filters as it as a plain EI transformer on the input and the transformer primary is the only load.  Also, the meter is a CAT I/1000V rated DMM and the front panel is nonconductive.  I measured the chassis leakage current on my example at less than 10µA.  At 220V I expect it will be a bit higher.  The real hazard would be that the OPs unit is damaged or has some malfunction, as the primary power input is present on bare metal parts inside the bare metal chassis with only some space and air between them.   If nothing goes wrong there's no real shock hazard but physical damage, moisture or a stray spider might change that.

[TimFox]

Assuming the power entry connection employs a standard three-terminal line filter:

This meter actually doesn't,  AFAIK (unless it is well hidden) and it just has a inlet/switch/fuse/voltage selector block all combined in one unit.  No need for filters as it as a plain EI transformer on the input and the transformer primary is the only load.  Also, the meter is a CAT I/1000V rated DMM and the front panel is nonconductive.  I measured the chassis leakage current on my example at less than 10µA.  At 220V I expect it will be a bit higher.  The real hazard would be that the OPs unit is damaged or has some malfunction, as the primary power input is present on bare metal parts inside the bare metal chassis with only some space and air between them.   If nothing goes wrong there's no real shock hazard but physical damage, moisture or a stray spider might change that.

That makes sense.  I can't find the manual for this unit online:  since all the possible power cords available for the unit are standard 3-prong plugs (for various jurisdictions), what does the "third prong" actually connect to inside the Fluke unit?

[bdunham7]

what does the "third prong" actually connect to inside the Fluke unit?

It is connected directly to the chassis via a short wire.

[TimFox]

what does the "third prong" actually connect to inside the Fluke unit?

It is connected directly to the chassis via a short wire.

With no capacitors between either line and that internal connection?

[bdunham7]

[TimFox]

What is the unit at the left of the photo, marked "KG"?

[bdunham7]

That's the part that holds the fuse and voltage selector block.  With those pulled out, you can see the unit is otherwise empty.  The only way I see to get any non-trivial leakage to the chassis would be via the transformer, which as you can see has a ground shield.  The entire board and front panel are isolated and floating with the exception of a small section where the serial port is connected and that is separated with optos and large gaps.

I found a link to the Schurter KG series IEC inlets:

https://www.schurter.com/en/datasheet/KG

The CG version with line filter is available as well:

https://www.schurter.com/en/datasheet/CG

[TimFox]

Thank you

[xlzslayer]

You don't need to get a Fluke-specific fuse (p/n 163030), but you do want the MDL 1/16.  These are commonly available here and the eBay ones typically aren't fake. Sure, a transformer will work, if it is an isolating transformer that's even better.

I see. Is an MDL fuse just a slow blow glass fuse of a certain size?

The meter is no more or less hazardous than other appliances and instruments that should be grounded.  The front panel inputs are all guarded (isolated) from ground or power and the only way the chassis would be energized is if there were a failure of the internal primary wiring (power switch and inlet) or transformer.  Without a ground the chassis could float up to some voltage or could have AC leakage current energize it to some potential but without much current.  This might cause increased residual counts in the AC ranges or give you a slight buzz if you handle the meter. 

Oh okay, glad to know that the front panel inputs are isolated, was a bit worried about that. Yeh small zaps from the enclosure won't be an issue, you kinda get used to it here since you grow up with some other appliances behaving like that, you start learning to put on some footwear or to not touch the wall etc. to avoid making a path to ground. A drift in AC measurements kinda sucks if true, but I care less about AC accuracy. Perhaps I can test how much it drifts by temporarily acting as a path to ground myself 


Thank you for the help, I really appreciate it! Do you think I should bother with adding any type of protections? As scary as it looks, I don't think the primary power input will end up causing issues, but that's just my unprofessional opinion. i could probably coat the bare metal or put an insulative sleeve around them?

[bdunham7]

I see. Is an MDL fuse just a slow blow glass fuse of a certain size?

It is a specific type of slow blow fuse that works well with small power supply transformers.  It is 3AG sized, so the old-school glass fuse dimenstions.  The MDL 1/16 or MDL 1/16R has a high enough resistance that it will limit fault current to <5A @ 220V even with a direct short and under those circumstances will clear the fault (blow) in less than 10ms or half a cycle.  Great protection against accidents but very rarely blow in normal operation.  Any 1/16A (62.5mA) slow-blow fuse would be OK, but I'm not sure what else there is.

Oh okay, glad to know that the front panel inputs are isolated, was a bit worried about that. Yeh small zaps from the enclosure won't be an issue, you kinda get used to it here since you grow up with some other appliances behaving like that, you start learning to put on some footwear or to not touch the wall etc. to avoid making a path to ground. A drift in AC measurements kinda sucks if true, but I care less about AC accuracy. Perhaps I can test how much it drifts by temporarily acting as a path to ground myself 


Thank you for the help, I really appreciate it! Do you think I should bother with adding any type of protections? As scary as it looks, I don't think the primary power input will end up causing issues, but that's just my unprofessional opinion. i could probably coat the bare metal or put an insulative sleeve around them?

As I said, the overall design is no more or less hazardous than everything else around your house that was intended to be used with a ground.  It is pretty high quality with low leakage, so I'd say if there's no physical damage and you keep it dry, you probably won't have a problem.  I'd still rather see you get a ground setup, but a GFI/RCD might be an acceptable substitute from a safety standpoint.

[golden_labels]

I don’t know, what system Lebanon uses, but in many countries old unearthed 2-wire systems were updated, so the neutral wire became neutral + earth. This is being done without touching apartment’s installation. So in most cases people never realized that: while they themselves were in work, electricians came and attached a few wires in the switchboard. If that’s the case, you only need to replace the outlets.

An electrician will be able to confirm, what kind of an installation you have. They’ll also mount new outlets for you.

A PEN wire is inferior, compared to separate N and PE. It also brings its own unique risk. But it’s still much better than no earth.

[tatel]

I'll be trying to get the exact fuse replacement required, but it'll be quite a bit later (a month or so). I didn't realize that fluke listed the exact part number for the fuse until recently, and said family member will be coming today-tomorrow for a few days and will be leaving again for a month or so. I can run the meter on a 120v transformer in the meantime, will that suffice temporarily?

We use an EU variant of the C13 that allows you to connect 3-pin equipment sockets into 2-prong outlets (check attached image). The grounding issue will be a bit difficult to fix, I live in an apartment and we use PVC pipes (or some other kind of plastic) for our water supply. I don't really have access to a grounding rod, nor do I have a place to plant one in the ground. Not having a dedicated ground hasn't been much of an issue for other appliances, just little zaps here and there, but the meter is a different type of instrument so it got me a bit worried after seeing that warning.

I'm probably missing something? That IEC you show has earth connection. Two prongs and that metallic strip. The jack should have two holes and a couple of metalic contacts. This is where earth connection is made. Of course, it could be that the electrical installation in your building is defective or anything.

[Kleinstein]

A PEN wire is inferior, compared to separate N and PE. It also brings its own unique risk. But it’s still much better than no earth.

When GFIs are used it very much depends and it could be preferable to not have PE connected.

[tooki]

We use an EU variant of the C13 that allows you to connect 3-pin equipment sockets into 2-prong outlets (check attached image). The grounding issue will be a bit difficult to fix, I live in an apartment and we use PVC pipes (or some other kind of plastic) for our water supply. I don't really have access to a grounding rod, nor do I have a place to plant one in the ground. Not having a dedicated ground hasn't been much of an issue for other appliances, just little zaps here and there, but the meter is a different type of instrument so it got me a bit worried after seeing that warning.

The image attached to that reply shows a standard grounded European (combined Schuko and French) plug.

[bdunham7]

A PEN wire is inferior, compared to separate N and PE. It also brings its own unique risk. But it’s still much better than no earth.

IDK if that's really an improvement here.  If the PEN system is all the way to the sockets, then any failure along the way results in floating up to mains voltage.  I think the meter is much less likely to fail internally than the electrical installation. 

[Terry Bites]

 Local ground is usually created by bonding to incomming neutral and internal metal pipework. Its not a wire from the electricity supplier. You can optionally bond it to ground stake outside.

If you have an identifiable neutral then thats the way to go.