Calibrating old instruments

[Wildcard]

I grabbed a few bits and pieces from an old print shop that had been out of business for years and finally getting rid of their dusty equipment. Among the things I picked up for a bargain was an old Stretch Devices tension meter, and an Atkins Thermocouple with one needle probe and 2 donut probes.

The tension meter seems good but I know they need regular calibration and servicing. The thermo probe needs a new battery and the probes look a little dusty and dirty. What sort of calibration, checks, or servicing would be required/recommended to make sure these instruments are giving reasonably accurate* results?

[tpitman]

Regarding the tension meter, as long as you can adjust the pointer to zero out by loosening the screw at the top while the meter sits on the calibration glass included in the case then it's within specs. I bought mine for $175 and had no glass or case. Sent it in and had it repaired, plus bought the case and glass. Not something I used day in and day out, but after about 12 years it's still within specs. I think I had to adjust the pointer a tiny bit once since I had it repaired.

[Maxie]

I have both of these and I bought them in 1994.
I took the Newman tension meter to Long Beach this year and had Don Newman test it against a new one.   It was  spot on.    Not bad after 23 years.    I do keep it in the original case when it's not in use.
Best way to test yours is to find someone with a accurate meter and see if it's the same.
Also with the Atkins donut, test it against a test strip or something else you know is accurate.

[Frog]

I have both of these and I bought them in 1994.
I took the Newman tension meter to Long Beach this year and had Don Newman test it against a new one.   It was  spot on.    Not bad after 23 years.    I do keep it in the original case when it's not in use.
Best way to test yours is to find someone with a accurate meter and see if it's the same.
Also with the Atkins donut, test it against a test strip or something else you know is accurate.

I never found the test strips consistently accurate, at least enough not to verify calibration of precision instruments.
If the probes can handle water, an easy test would be to confirm the boiling point.

[jsheridan]

 You have to calibrate the Atkins donut probe with ice water.
Start here..
http://www.cooper-atkins.com/Resource_Center/

As long as the meter has not been dropped.. check all the edges for signs of mushrooming that would indicate metal landing on concrete it's good to go for basic tension under 40n. Calibrate it in plate glass like TPI said.

Nice score!

[Wildcard]

Thanks! All responses helpful.
Ashamed to admit I never thought to self-calibrate with ice or boiling water... I guess there's no risk of shorting those little cross wires since they can touch anyway.

Tension meter seems in good condition and I did zero it out on the little marker, but I think the mechanisms/needle may seem a little sticky after so long out of action? Truthfully though, I'm not at the level of needing it to be super accurate as pointed out by jsheridan, just wondering what TLC might be good for these pieces.
Really pleased to have these!

[Maxie]

John thanks for the info.

[spotcolorsupply]

Best way to test yours is to find someone with a accurate meter and see if it's the same.

I tend to agree with Maxie... Just because you set it to read zero on the glass, IMHO doesn't necessarily mean its right. Or just send it to newman for calibration..

The last time we did, they even marked one side of the glass that should be used.   

[Wildcard]

Best way to test yours is to find someone with a accurate meter and see if it's the same.

I tend to agree with Maxie... Just because you set it to read zero on the glass, IMHO doesn't necessarily mean its right. Or just send it to newman for calibration..

The last time we did, they even marked one side of the glass that should be used.   

Yeah, I'm a little out of reach of any major supplier that could test and service these things.
Would a watchmaker or precision engineer be able to work on the tension meter?

[Maxie]

You can open and clean the inside and lightly oil it.
Check against someone else's, even if you find that it's a little out you can still use it.   You'll know how much it's out.   Chances are it will be constant and not fluctuate.
I think it's more important o be constant and not exact

[blue moon]

You can open and clean the inside and lightly oil it.

DO NOT open or apply oil anywhere in there!!!!!!! As a watchmaker (hobby) I can tell you that the amount and type of oil you put in will impact the readings. You need to know the proper viscosity and makeup of the oil that goes in there. If it is anything like a watch (which uses 4 or more different oil types depending on the loading of the gearing) it needs to go to a calibration shop. Additionally, the new synthetic oils do not evaporate and will last almost indefinitely with the amount of use the meter gets.

My suggestion would be to order a screen from your suppliers and have them measure the tension. Then you can compare it to your meter when you get the screen. It is not perfect, but will help and will cost very little.

pierre

[GaryG]

Ahh a hobby watchmaker- no wonder you dial in those prints for awards! 

[mk162]

Or better yet, send the meter to Pierre and let him fix it.  It's a hobby, so he won't charge you anything.

[Wildcard]

As a kid I rarely managed to put things I took apart back together properly... so I'm not taking my chances with a tension meter!

I need screens re-meshed anyway so I'll do a soft calibration that way as suggested.

I'm not stretching screens, so the meter will only be to monitor screens in use which won't need the full accuracy.