[volt-nuts] Fluke 732A Questions

[Charles Steinmetz]

Joe wrote:

>Also, how do you get your 732A calibrated?  Do the batteries last long
>enough to ship overnight to a facility?

No -- I assumed that was why you were looking for a battery 
connector.  You install an external battery for shipment 
overnight.  Fluke can supply a complete external battery with cable 
and plug ($375, last I knew), or you can make your own.  I believe 
they can also supply a shipping container, which has a dedicated 
space for the Fluke external battery.  (If you don't use Fluke's 
container, build something very sturdy with wood and padding and with 
handles that make it hard not to carry it and set it down right side up.)

I wouldn't have anybody but Fluke calibrate a 732A.  There are 3 
levels of calibration, all with data, from about $700 to about $1500 
(the last is calibration by Fluke's Primary Standards Lab).

As far as thermistor values go, the relevant question is not what is 
the value in absolute terms, but rather what is the value in relation 
to the "as manufactured" value, which was provided by Fluke when the 
unit shipped.  This had been recorded by the original owners of each 
of my units, and they are all within 2 ohms of the original value today.

If you do not know the original value, then your original measurement 
is a "going forward" value and it cannot tell you anything about 
where you are in relation to  the original manufactured value.  The 
fact that you had to change cal jumpers suggests that either the oven 
temperature has shifted since manufacture, the reference assembly has 
shifted, or both.

Fluke has said various things in various places about how far the 
thermistor readings can drift before you have a problem.  +/- 20 ohms 
over the unit's lifetime seems to be a good consensus value.  If it 
changes fast -- say, 10 ohms or more in a month -- you have a problem.

Best regards,

Charles