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 Post subject: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 12:03 am 
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Joined: Jan Mon 16, 2017 3:08 am
Posts: 130
Location: Boise, Idaho
I sent in a 410B to be rebuilt because I did not have all the equipment to properly calibrate per manual but mostly to save me time. I received it back and it was not right...reading 92 volts AC when all my other equipment, (Flukes, B&K, RCA VTVMS) including two newly calibrated Simpsons done by IMS, were reading 115. This was after letting it warm up for like 45 minutes.

This is what I am being told: It is on our bench, going to let it stay powered on for a week or so , checking calibration from time to time. So far, nothing unusual noted

Huh? Going to leave this equipment running 24-7. That seems like a recipe to cause a tube or transformer failure...am I wrong?


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 1:17 am 
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Location: Monte Vista, CO. USA
Is that an HP 410B? Those are designed to be in use 24/7 in a production environment, so it won't hurt it.


Last edited by PhilF on Jul Mon 17, 2017 1:19 am, edited 1 time in total.

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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 1:18 am 
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Many labs and repair shops left their equipment powered on 24-7 for years with no issues. That should not be a problem with well designed, quality equipment.

However, I would never do that at home because there's always the slight chance that a power surge or lightning strike could damage it when no one is around to turn the power off. It also runs up the electric bill.

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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 1:20 am 
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Me thinks its time to see if the performance warranty is any good. I would accept 114.9 or 115.1 but 97???

Let us all know if there is satisfaction...

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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 1:37 am 
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Location: Santee Calif. 92071
No need to leave any test equipment running all the time. A master shut off switch on your work bench should be used. Can turn on the mater switch in the mornings if you plan to work on something that day. Have a cup of coffee. By the time your coffee is done all test equipment is ready for the day.


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 1:40 am 
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I've worked in many labs that left the equipment on continuously.
That does NOT mean that the readings changed over time.

In fact, it was done so the readings would NOT change over time.
We usually figured the stabilization period was about half an hour, and allowed that before use.

- Leigh

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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 1:43 am 
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FWIR EICO and I'm kinda sure other test manufacturers (kits) suggest a "burn-in period" before calibration. Repeated when any critical component or tube is changed...

Chas

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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 1:51 am 
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Location: Monte Vista, CO. USA
thunderbird281 wrote:
No need to leave any test equipment running all the time. A master shut off switch on your work bench should be used. Can turn on the mater switch in the mornings if you plan to work on something that day. Have a cup of coffee. By the time your coffee is done all test equipment is ready for the day.


I have a HP 3336A generator that has the oven option. Its maximum accuracy is obtained only after 48 hours of power. You don't have to leave the generator on, but it does have to be plugged into a powered outlet continuously.


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 2:10 am 
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I don't see an issue with solid state gear, assuming no damaging power surges on the line or something. And working in an air condx. environment with room for air around it, no other hot gear under or on top. I have left on some gear by mistake and come in later in the week to discover this. No harm. What I do not run constantly is an item that might have components that deteriorate. Displays, CRTs, tubes, etc. And my Rubidium freq. standard. I only power it up when needed as the main reference supposedly has a limited lifespan. It of course would be ideal for it to run all the time probably, but that would only make a completely indiscernible variation more-so, for my purposes. But if you are not in an industrial environment, there is no need to waste the electricity. Just allow maybe some time before lab grade testing with super accurate gear. Your meter seems to be rather low regardless of warmup time. I guess it depends on your reference but let it burn in and then talk to the lab!


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 2:25 am 
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Location: Boise, Idaho
At least I feel better about them leaving it on for a prolonged period. I would never do that at home though.

I understand the margin of error in these things but I question the calibration of their equipment at this point if they are telling me there is nothing wrong. At 30v, on 30v scale it would read just about 28, needle just hitting the 28 bar.

When I bought my Simpsons the guy told me "I calibrated them myself with my Simpson 270's, so don't touch them". I was getting all kinds of inconsistencies against my Flukes and B&K so I sent them in to IMS. They found all kinds of out of tolerance resistors. Here is a plug for IMS....the did a KILLER job. Quick turnaround, excellent updates. I highly recommend them. My Simpsons are spot on now and I completely trust them. The 410B I sent out I would not trust to check voltage on my car battery.


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 3:36 am 
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Reading 92 volts AC on what? An isolation transformer? Or the power line directly? If the latter, I assume you left the probe ground unconnected. Did you measure the same branch circuit that the meter was plugged in to? If so, then what reading do you get when you probe the neutral?

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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 3:50 am 
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Location: Boise, Idaho
Power signal was: wall to variac to isolation transformer. I was taking reading off isolation transformer.

VTVM powered by separate Isolation transformer via same circuit but off another outlet on opposite side of the room.


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 4:55 am 
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Your measurement setup looks good. One final possibility would be that the waveform for some reason had lots of harmonic distortion. Since the 410B is peak reading while the Simpson s are average reading, that could cause a discrepancy. But you say other VTVMs also read the same as your Simpsons, so that rules out the waveform.

You're reading it on the 300 volt scale. AC accuracy of the 410B is spec'd at +/- 3%, or 9 volts, so reading 97 is far out of spec.

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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 5:29 am 
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Location: Charleston, W.Va.
Leigh wrote:
I've worked in many labs that left the equipment on continuously.
That does NOT mean that the readings changed over time.

In fact, it was done so the readings would NOT change over time.
We usually figured the stabilization period was about half an hour, and allowed that before use.

- Leigh

+1 to above comments by Leigh. I could not agree more. As he says, when leaving test equipment run 24/7 their readings should not change over time, but rather remain stable.

The above being said, and since I have a small one-man shop and thus don't use all of my test equipment on a daily basis, I do not usually leave them powered up 24/7. Not that my test equipment is not capable of withstanding it, but rather to extend their life. Also no reason to expose unused powered-up test equipment to the remote possibility of power surges, lightning strikes, etc., as others have mentioned.

And exactly as Leigh and others have said, I find that about a half-hour warmup period should be adequate to stabilize any service-grade test equipment (whether tubed or solid-state) which is otherwise in good condition. Of course this is for typical service shop work; the same would not necessarily apply to test equipment used in a lab setting.

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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 12:04 pm 
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Joined: Apr Mon 10, 2017 12:11 am
Posts: 11
I currently have worked 33 years at my present location, and we do not leave equipment on overnight,
unless we are charging battery packs that require 16 or more hours to fully charge.

We rely on our Fluke and Tektronix meters and scopes, the Simpson and 410B have been retired
years ago, but they still work. I would suspect a failure of some sort with the reading you are getting.

If it were mine, I would use the new meters only, and retire the old 410 and put it on display.

40 years ago, I worked at a shop where we left a Lampkin 105B frequency meter on 24/7, but that
was antiquated then! The new 'digital' frequency counter was the suspect devise, as the old techs said
it wasn't lab quality as the Lampkin 105B! Our new digital synthesized equipment is instant on, with no
oscillator ovens or other requirements, other than the power on self test.

N8CMQ Jeff


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 1:05 pm 
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Location: Long Island
Most commercial test gear is designed for 24/7 operation. I give my test instruments a few days to a week of "on time" every year or so to ensure the electrolytics stay formed. And it should be noted that some instruments stabilize in half an hour but there is no hard and fast rule on that. Some things require more time to stabilize, especially when they are getting old. Know your equipment!

With regards to the HP 410B, you need to get in touch with whoever calibrated it for you. 92 volts out of 115 is more than just a warm-up problem. As an AC voltmeter that can operate well into UHF, it has some characteristics that few other instruments ever equalled. Mine will read 115 on 115 volts at 60-Hz (and I measure off the secondary of an isolation transformer too).

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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 1:23 pm 
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Joined: Jan Mon 16, 2017 3:08 am
Posts: 130
Location: Boise, Idaho
I had no systematic method while I was testing it out. Simply changing the variac, switching between meters and changing the range switch. Some ranges were spot given the same input voltage, other times not. It was very time consuming switching between 4 and up to 7 meters a few times. I was happy with the 98C and 98A I rebuilt as they were dead on or within spec.

This is all sport and fun for me. I don't do it for a living so I am learning as I go. Due to my wife's health I usually only have an hour or two a day to work on things; which is why I sent this out...save time and frustration. I really enjoy using the VTVM's from time to time for nostalgic reasons (?), and use them exclusively during the alignment process. Other than that they mostly sit and look pretty. I simply prefer the 410B meter movement over the RCA's, though my favorite meter face is the 98A

I am rebuilding a 200CD now and then I will pick up a good capacitor checker that will do leakage, and then something to check coils..henry's, go through that that scope that was given to me....and then I think my test equipment lineup will be done and I can turn my attention back to these receivers and transceivers I keep collecting.

SO much knowledge on this site....I appreciate all that are here and participate!


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 7:49 pm 
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Joined: Feb Mon 20, 2017 7:21 pm
Posts: 140
Why leave any thing on
Would leave car running 24/7
My self I used a voltage stabilizer

Dave


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 8:25 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 10839
Location: Mpls, Minnesota
smithdoor wrote:
Why leave any thing on

Test equipment is left on to stabilize temperatures and reach a equilibrium.
smithdoor wrote:
Would leave car running 24/7

Diesel trucks are left running,any large engine is kept running,trains, power plants, ships,etc. Heating and cooling cycles are not good for large machinery.
smithdoor wrote:
My self I used a voltage stabilizer

That will not stabilize the temperatures

Dave


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 Post subject: Re: Leaving equipment on for a week or so
PostPosted: Jul Mon 17, 2017 10:32 pm 
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Joined: Feb Mon 20, 2017 7:21 pm
Posts: 140
Buy heater and save your test equipment (off)
The Diesel left on do to lack of maintains on the air brakes and or the engine needs work too
You also may your CPU on too I have switch that turns all power when I leave the room.

My equipment has lasted over 50's and still working today

Dave

easyrider8 wrote:
smithdoor wrote:
Why leave any thing on

Test equipment is left on to stabilize temperatures and reach a equilibrium.
smithdoor wrote:
Would leave car running 24/7

Diesel trucks are left running,any large engine is kept running,trains, power plants, ships,etc. Heating and cooling cycles are not good for large machinery.
smithdoor wrote:
My self I used a voltage stabilizer

That will not stabilize the temperatures

Dave


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