Fluke A55 3V Thermal Voltage Converter - I Need Inputs

[Hawaii596]

I'm getting ready to pull a couple of TVC's out of mothballs.  I have a 1 volt Ballantine (1395A-1), and also an old Fluke A55 3V TVC. 

Ballantine, no questions.  Sending it out.

However, regarding the Fluke A55, does anyone know (relative to a Ballantine - generally speaking) how good the Fluke A55's are?  I'll probably end up looking it up anyway.  My Ballantine is 1V and the Fluke is a 3V.  Just wondering if the Fluke is comparable and worth making it my 3V alongside my Ballantine as my 1V.

P.S. - Different topic... I JUST sent my guildline 9975 out for repair (its been mothballed for a very long time).  Getting ready to get resistance on line.  Exciting, eh (and not a Canadian "EH" either)?

[michthai]

For best accuracy send them to NIST (expensive).   You can look up on the NIST accuracy(s) on their website.  All thermocouples are good until someone applies excessive input.   Like a fuse, they are very unforgiving.

[WestCoastCal]

Presumably you are using them for flatness measurements, our 1395's have been rock solid (except when overvoltaged-that's when I make a necklace of the thermocouple and present it to the offender).  Don't know much about the A55's though but recommend you get them both cal'd as generators are often spec'd at different voltages, thats a lot of ground between 1 V and 3 V.

[LarryH]

I concur, you need to have both available: 1V and 3V.  When you are dealing with mV outputs from these, you can easily get into the noise floor of the 3v TVC and not be able to resolve your readings.

I would check them before sending them out - make sure you have a good, solid mV output across the freq span (10Hz to 10MHz).  IF they do, they should calibrate fine.

[scottbp]

P.S. - Different topic... I JUST sent my guildline 9975 out for repair (its been mothballed for a very long time).  Getting ready to get resistance on line.  Exciting, eh (and not a Canadian "EH" either)?

Where did you send it? Guildline? MI? We have an old 9975 kicking around in our warehouse I'd like to revive one day.

[Hawaii596]

I shipped it to Measurements International.  They apparently have a stock of old 9975 units they use as trade ins when people buy their new MI models.  If you send me a private message, I'll give you the person's email address I communicate with about it.

Mine was pretty pricey (got the quote - they already know what is wrong with it).  However, I apparently had a transformer short and send a large surge and blew out numerous power supplies.  I'm waiting on upper management to approve the P.O. to pay for it, and (if they approve), I should have it back in a few weeks.

[purpmcrider]

I'm not sure if you still need information on the Fluke 3V A55.  The Fluke PSL should still be supporting the calibration of the A55 and they can give fairly good uncertainties.  The A55 has specs similar to the 1395 type converters as well as the 11049, 11050 and 11051 and the MeasureTech equivalents.  The big difference with the A55 is the input resistance.  While all the others are 50Ω units the A55 family of convertors are 5 mA and about 180Ω/V.  My memory may be faulty and it's really 90Ω/V, but I think I'm remembering correctly.

You need to consider the input resistance of the TVC and what that will do to your calibration.  Hope this helps.

[michthai]

FYI, you can get replacement thermocouples from Best Technologies (besttech.com) and complete units from their sister company Measure Tech (measure-tech.com). These are top of the line parts and complete units. The technology they are using now provides very high precision and with very low reversal errors.

[Pylarinos]

I think that is a usefull thermal converter especially when you are calibrating flatness of a synthesizer up to 50MHz.
It can be used also with the 540B thermal transfer STD.
It has to be calibrated from a higher laboratory which can provide a calibration fron DC to 50 MHz, propably a NMI.

[WestCoastCal]

A 540B?  is anyone else still using one?

[Hawaii596]

I am setting up my standards lab and have a 792A as primary AC.  But I also have a 540B which I'm not sure yet whether it works.  It had one of those mercury batteries in it that looks almost like a D cell that was shot.  I need to replace that before I test it.  I am thinking of using the 540B as an intermediate check box, and the 792A as the primary.

[Pylarinos]

I think that this is a good idea...

[measure]

I'm not sure if you still need information on the Fluke 3V A55.  The Fluke PSL should still be supporting the calibration of the A55 and they can give fairly good uncertainties.  The A55 has specs similar to the 1395 type converters as well as the 11049, 11050 and 11051 and the MeasureTech equivalents.  The big difference with the A55 is the input resistance.  While all the others are 50Ω units the A55 family of convertors are 5 mA and about 180Ω/V.  My memory may be faulty and it's really 90Ω/V, but I think I'm remembering correctly.

You need to consider the input resistance of the TVC and what that will do to your calibration.  Hope this helps.

purpMCrider makes several good points that anyone using A55s should be aware of:

• Their input impedance is 91 Ω/V (5 mA). Some of the other models mentioned have fixed input impedances at 50 Ω, 75 Ω, 600 Ω, etc.
  
• Fluke still supports the A55 with quite good uncertainties
  
  • Hawaii, you don't say what your intended application is for the A55, but unless the impedance is a problem for your specific measurement (it may be), the A55 is a solid unit
    
  • Replacement TCs are available (as mentioned) from besttech.com, and measure-tech.com will actually repair the units as well (not sure if Fluke still repairs them, though they DO still calibrate them)
    
  
  Good Luck!

[Hawaii596]

I sent both my TVC's to Ballantine.  We are part of a new company now, and have more TVC's; so I'll have to re-think it a little.