[volt-nuts] A Fluke 732A: Return it or keep it?

[J. L. Trantham]

Michael,

I would recommend you download the manual if you have not already done so.
(Sorry, just noticed you had looked at the manual.)

I don't think you are going to have enough resolution with the 3457A to
characterize the 732A, other than a rough idea of stability.  You will need
a 3458A, a Solartron 7081 or some other 8 1/2 digit DMM.

The unit uses four 6 V SLA batteries that are relatively cheap.  I ordered 8
of them since shipping was the same, whether I got 4 or 8.  Unless they were
recently replaced, you will need to replace them.  The 'In Cal' light needs
to be 'reset' after the unit is powered up, stabilized, and calibrated.  It
remains on as long as there is continuous power applied to the unit, either
from AC, the battery pack, or an external battery attached to the connector
on the back.  I have a spare connector, yours for cost plus shipping, if you
need one.  Two others on the list have sent me the money for one but work
has really interfered with my life this week and I have not yet shipped
them.  It will be tomorrow.  (Sorry, guys, my apologies.)

The batteries I ordered are these:
http://www.batteryclerk.com/store/p/80492-Panasonic-LC-RB064P-Sealed-Lead-Ac
id-AGM-VRLA-Battery.html  $5.69 each plus shipping.

If power is lost, power must be re-attached and the 'In Cal' light 'reset'.
The light is 'reset' by connecting the negative terminal to a spot in the
'reset' hole just below the 'In Cal' light.

If the battery charge light is not on, and the unit is plugged in, the
batteries are either completely charged, not connected, dead, or there is a
problem with the charger circuit.  My bet is a battery issue since I bet you
had to plug in the unit to get it to work.

There is a multi-turn pot inside each of the three holes and they are
difficult to get to but can be seen if you have a flashlight to shine in
essentially parallel to your line of sight.  If the 10 V can't be brought to
exactly 10.0000000 V, there are 'jumpers' under the top layer of insulation
for the 'heated unit' that can be adjusted to bring it 'in range'.  At least
I was able to bring mine 'in range' and 'calibrated' against my Agilent
Cal'd 3458A.  Mine has been on continuously now for about 2 months.  I
'calibrated' it after it was on for about a week.  It now reads about
9.9999920 V and seems extremely stable (3458A with NDIG=8 and NPLC=60).  I'm
thinking of 're-calibrating' it and see how close it will stay to 10.0000000
VDC.  I think it will be more stable the longer it is on.  I have no idea of
how long it was off before I turned it on.

The schematic of the A5 Reference PCB Assembly shows the calibration
adjustments and the drawing of that assembly shows the location of the
adjustments.  They are deep inside the unit.  You'll need a small flat
bladed tool, a flashlight, and probably a magnifier.  I used a length of 12
ga. copper wire with one end flattened to make a screwdriver.

Good luck.

Joe

-----Original Message-----
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
Behalf Of Michael Hong
Sent: Friday, March 07, 2014 6:19 PM
To: volt-nuts at febo.com
Subject: [volt-nuts] A Fluke 732A: Return it or keep it?

Hi nuts,
This is my first message. Just reading the posted messages is a big learning
to me so I didn't post but instead trying to read all.

Here is my issue.

I received a Fluke 732A yesterday which was purchased from an eBay seller.


(1)
I plugged in and started measuring the 3 voltages and thermistor resistance
value.
After about 2 hours later all 3 voltages were stabilized and thermistor
value stabilized after 24 hours.

All voltages and thermistor values were measured on a HP 3457 which was
calibrated and certified by a local cal lab 10 months ago. Here is how I
measure: After changing the connection to a different voltage I wait 30
second. I start STAT and wait 1 minute and R MEAN.

10V      (10.000360 36.0ppm, 360uV)
1V        (1.0000383 38.3ppm, 38.3uV)
1.018V  (1.0180200 20ppm, 20uV)

According to the manual adjustable(calibration) ranges are:
10V     5ppm 50uV
1V       5ppm 5uV
1.018   50ppm 50uV

So obviously either 732A or 3457A is wrong.
I tried to contact the person who calibrated the HP 3457A. No response. 

(2)
No light on BTRY CHG and IN CAL
Rear panel Battery Operation switch is on.

(3)
Front panel calibration hole
I put a thin flat blade driver into the holes. I couldn't feel anything
until 4 1/4" inside where I felt something but not the potentiometer.



I offered to the seller that if I find the 732A is no problem but only
requires the new battery, refunding $150 for the battery will close the
deal. All other case, I return the item. 

He responded "Just return it."

My questions:
(1) Which one is wrong the DMM or 732A?
(2) What is the cheapest battery replacement cost?
(3) Were the calibration mechanism removed or they are there? In manual I
couldn't find any detailed description or diagram of it.

Last, I paid $650 plus $35 shipping. Do you think it is worth without
battery, if voltages are in the range?

Michael
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