Ekg

[sparkyjpb]

A doctor's office is having problems with the EKG machine working in all rooms. The original office was built in the late 60's/early 70's and the "new" portion in the late 70's. The machine never fails in the new portion but it's hit or miss in the old section. They have taken the machine offsite and it never fails. It's even been sent to the manufacturer for inspection. Came back ok. Help!

 

[TOOL_5150]

Were going to need to know a little more info than what you provided. Whats the voltage? What kind of panel is it? Have you checked the neutrals? Is the receptacle old, maybe it is not gripping the plug properly and causing a bad connection.

~Matt

 

[ItsHot]

dedicated circuits

dedicated circuits

You may need dedicated circuits, so you do not have "something very screwy" with the neutrals!:grin:

 

[brian john]

You may need dedicated circuits, so you do not have "something very screwy" with the neutrals!:grin:

This may not solve the issue. If there is ground current the new cable EGC may/will carry some of the ground current.

If you have neutral ground issues you need to locate them.

1. Do you have a Gauss meter?
2. Use the Gauss meter to check for EMFs, a good sign of neutral issues.
3. Use a clamp on and take zero sequence measurements on the panel feeders all phase and neutral simultaneously, the reading should be ZERO "0".
4. Measure current on the neutral to ground bond jumper. This should be "0" or close to "0".
5. With the power off, lift all branch circuit neutrals.
6. Unplug all equipment and turn off all lights.
7. Megger the neutrals to ground at 100 VDC then 1000 VDC, an ohm meter will suffice but a megger is perfered.
8. All neutrals that megger "0" or have questionable readings should be investigated.

 

[ARF]

[

QUOTE]

A doctor's office is having problems with the EKG machine working in all rooms. The original office was built in the late 60's/early 70's and the "new" portion in the late 70's. The machine never fails in the new portion but it's hit or miss in the old section. They have taken the machine offsite and it never fails. It's even been sent to the manufacturer for inspection. Came back ok. Help!

[/QUOTE]

When you say hit and miss do you mean that plugging in to the same receptacle in the old section produces the same result or, plugging in to various receptacles is hit and miss?
While checking out neutrals you might also want to check out the receptacle's polarity and grounding.
Good Luck.

 

[Buck Parrish]

Late 60's early 70's


Hmmm, That's about the time aluminum branch circuit wiring was being used.

 

[sparkyjpb]

[

When you say hit and miss do you mean that plugging in to the same receptacle in the old section produces the same result or, plugging in to various receptacles is hit and miss?
While checking out neutrals you might also want to check out the receptacle's polarity and grounding.
Good Luck.[/QUOTE]

It's hit or miss for the EKG to work anywhere in the old section. There's no one outlet in the old section that it will always work in, or not work in, for that matter. They regularly move it from room to room and there's no rhyme or reason to where /when it'll work.
The machine's portable so they have to roll it to the new section the times that it goes nuts in the old.
No AL wiring, all copper.

 

[sparkyjpb]

This may not solve the issue. If there is ground current the new cable EGC may/will carry some of the ground current.

If you have neutral ground issues you need to locate them.

1. Do you have a Gauss meter?
2. Use the Gauss meter to check for EMFs, a good sign of neutral issues.
3. Use a clamp on and take zero sequence measurements on the panel feeders all phase and neutral simultaneously, the reading should be ZERO "0".
4. Measure current on the neutral to ground bond jumper. This should be "0" or close to "0".
5. With the power off, lift all branch circuit neutrals.
6. Unplug all equipment and turn off all lights.
7. Megger the neutrals to ground at 100 VDC then 1000 VDC, an ohm meter will suffice but a megger is perfered.
8. All neutrals that megger "0" or have questionable readings should be investigated.

No, I don't have a Gauss meter.

 

[sparkyjpb]

The old section is on a 120/240 100 A sub panel fed by 2 hots, and a common neutral/ground run through EMT. The grounds and neutrals were originally not split. I separated them and made the pipe my grounding conductor. Back at the main panel, which feeds the sub and the new section, I ran a #6 copper to an existing ground rod. Existing because the entire service is in a basement and not on or near any outside walls. The ground rod is in the concrete floor and was put there for another panel from a separate service for a different office that is in the same building. That panel is for a dentist office.
After I did this, the problem seemed to be gone for 2-3 weeks. Thought it was fixed. Maybe just lucky for that time. Hope this sheds some more light.

 

[sparkyjpb]

Today I checked neutrals in the panel, in the outlets, and the main disconnect and CT cabinet. The CT neutrals were somewhat loose, they took a few good turns of the ratchet but I don't think they were so loose as to cause a problem. All else was good.

 

[JRTexag]

Gentlemen,

A little bit of informantion about the EKG machine would have helped identify the electrical problem a little faster The device uses a differential amplifier.

Each patient conection called a lead, of which there are 12 on the EKG mach;ine, consist of the following electrode leads: (+) , (-) and a ground. The positive electrode is one input of the diferential amp and the negative is the second input of the amp. The ground lead is attached to amp ground. The EKG signalis the millivolt difference between the positive and negative electrode is referened to the ground electrode. Lose the ground lead from the patient or the machine ground and the signal goes crazy. Lose the ground continuity from the machine to the ground pin of the plug is the same a no ground at the receptacle.

There are more circut components in the machine related to signal processing and patient safty but this information is what the EKG machine requires for proper function.

Given the previous post and the age of the other rooms electrical history my immediate conclusion was loss of ground. Floating earth ground will also give the same problems with the EKG machine but would not be isolated to a few rooms and be random.

Please be aware that medical devices require that special consideration be given to quality of power and grounding issues. A good sourrece of information may be the local hospital's Biomedical Technicians. They are responsible for the electical safety of medical devices in critical patient areas

Knowing what is at the other end of the plug helps with what is before the plug.

I hope this was helpful.

JRTexag

 

[iwire]

Given the previous post and the age of the other rooms electrical history my immediate conclusion was loss of ground. Floating earth ground will also give the same problems with the EKG machine but would not be isolated to a few rooms and be random.

What is your definition of 'loss of ground' or 'floating ground'. Different people use those terms in different ways.

Before we can discuss we need to understand each other.

By the way, Welcome to the forum. :smile:

 

[JRTexag]

What is your definition of 'loss of ground' or 'floating ground'. Different people use those terms in different ways.

Loss of ground in my understanding is a break in the path to earth ground as in a broken ground pin in a plug.

Floating ground as I visualize it as a ground with intermittant continuity. A loose and variable connection to the ground electrode would fit my understanding of the term.

An OPPs on my part. The amp ion the EKG machine is a push- pull amp not a differential. As a novice in this forem I do not know how to edit after posting

 

[Billy_Bob]

To edit, just click on "Edit" which will be in the lower right corner of your posts only.

Then what specific problems were they having with the EKG machine?

I'm not familiar with these machines, but if grounding is not a problem, other testing you can do is to run an extension cord from a "new portion" outlet with the machine located in the old section and see if they have problems or not. And do the opposite. This would isolate the problem to the room in which the unit is located or to the outlets.

Sometimes problems with sensitive equipment can be in the "air". Maybe a private radio communications antenna next door which is sometimes used, but the new portion is far enough away to block these signals. Or maybe the old portion is near the waiting room and people sometimes use their cell phones and this is causing problems.???

 

[cadpoint]

Brian, could you expand on the gauss meter.
I researched and read more about the inventer than the device itself, any books or lite reading, insights, overview, Etc ?

Thanks in advance