Joe, Bill and Charlie
Thank you all for your advice, and for the short term I will leave the 732A
as is. Like you Joe, my 732A arrived with a set of 'dead' SLA batteries -
these were replaced, and its been powered 24/7 since last October, again it
came with no history. I bought mine from a dealer on the West Coast who had
a batch of 14, so I guess that they came from a lab. Its stability is
impressive, and the Thermistor reading is currently 4.5194 K ohms, with only
small variations over time.
My 3458A had a new processor/RAM/ROM board fitted by Agilent - so it has the
latest 'plug-in/power-up' devices which I understand are a great
improvement, and was calibrated just about six weeks ago. I take your point
that the 3458A should be power continuously, but of course the display is of
the fluorescent type which deteriorate over time. This is now less
important, as I have had a new display installed, and the improvement is
great. I certainly agree that the 3458A is very sensitive to temperature
changes and as you advise, I frequently run 'Auto Cal' . I consider the
cost of its refurbishment/calibration to be well worth while, considering
the cost of a new instrument.
Best regards.
Roy
-----Original Message-----
From: J. L. Trantham
Sent: Saturday, June 14, 2014 1:48 AM
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] A Fluke 732A: Return it or keep it?
Roy,
The tool needed to adjust the 732A is both a tool with a recessed metal
blade and a tool with an exposed metal blade. The 10 V adjustment is
certainly the one with the recessed metal blade. The other two use one of
each. I just can't remember which is which. However, if you look at the
service manual (downloadable from Fluke or other sites) you can tell which
is which. All are a 'good ways' in the unit. If you get 'eye to eye' with
the adjustment holes, with a flash light, you can tell what the position of
the 'blade' should be to make the adjustments. Once properly 'in place',
leave the adjustment tool in position and wait a day or so to make sure all
remains stable. Don't forget to 'AutoCal All' the 3458A at least every 24
hours (leaving the 732A and the 3458A on 24/7) while doing this.
My experience with these standards is from a 732A and a 735C. They share a
lot in common. The 735C is 10.00000 V only.
Both my units arrived with dead battery packs (NiCd for the 735C and SLA for
the 732A) and no history of performance. When I 'resurrected' them they
were both way off scale. Since I had no history of their prior performance,
I decided I would allow them to 'settle' then adjust them to be 10.0000000
VDC as best I could do with my Agilent Calibrated 3458A. Both required
making adjustments to their internal 'connections' in order for them to be
'on scale' with the external adjustments. Once adjustments were made, I
have covered the access holes for the adjustments and the 'reset' hole with
tape to minimize ambient air currents.
Both are now very stable. With the 735C, for instance, when I 'AutoCal' the
3458A and read the voltage, it is +/- 1 uV from 10.000000 VDC repeatedly.
Tonight, for instance, it reads 10.0000001 then settles on 9.9999998. Both
the 735C and the 3458A are on 24/7/365.
I take that as evidence that they have 'stabilized'. My plan is to send my
Opt 002 3458A to Agilent for their 90 day specification Cal then use it to
do a 'final adjustment' to both the 732A and 735C. Once I'm confident that
both have 'stabilized' (which I hope will happen within the 90 day Cal
period), then I hope to send both to Fluke for their 'calibration'.
Once done, my plan is to never adjust them again but, rather, keep track of
their readings with a 3458A.
I agree with others that it is best to track the values rather than to try
to 'adjust' the references. However, if you have no 'history', you get to
start from scratch, or at least that's my opinion.
The 3458A should be about 4 PPM. Hopefully, the Opt 002 with a '90 day
Cal', it will be more like 2 PPM or better. We'll see what Fluke does with
the 735C and 732A, once they have a chance to take a look. Once
'calibrated', I agree it is more important to make sure they are 'in range'
and stable rather than trying to 'adjust' them each time they might go in
for 'cal'.
Hope this helps.
Good luck.
Joe
-----Original Message-----
From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
Behalf Of Charles Black
Sent: Thursday, June 12, 2014 11:18 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] A Fluke 732A: Return it or keep it?
Hi Roy,
I would like to second Todd's advice about leaving the Fluke 732A's output
voltage adjustment alone. You already have stable outputs and 24 microvolts
high is very acceptable. My Datron 4910 (four output supply) has predictable
digital output level settings that doesn't have any luck involved so it is a
better candidate for resetting the standards than the Fluke 732A. I had
Fluke reset them last calibration because I had just repaired the Datron
4910 and my voltages were all over the place but stable. Also I would
expect your Fluke 732A to about as temperature stable as my Datron 4910. In
my experience my 3458A needs to be at 23C to calibrate. Also it should have
the fan filter freshly cleaned and record the 3458A's internal temperature.
I have recorded (over several
days) each Datron 4910 output with my 3458A and a switch and can say that
the Datrons are temperature stable but not my 3458A.
Charlie
On 6/12/2014 7:54 AM, Bill Gold wrote:
Roy:
I use a ( General Cement ) GC 8276 adjustment tool to make the
pot adjustments in the 732A. I use the end that has the recessed metal
blade.
The pots are about 3.5 inches back from the front panel. It sometimes
is very difficult to engage the tool slot in the pot. It helps to
look through the front panel hole with a small flashlight and observe
the position of the slot in the pot ( i.e. 9, 10, 11 o'clock for
example ). Then when you insert the adjustment tool you can get close
to the point when you can engage the adjustment pot. Sometimes it
will seem impossible to engage the tool into the slot, but with
patience it can be done. Once you do engage the pot do whatever
adjustment you want, don't pull the tool out, just leave the tool
engaged with the pot so that if you want to make another small change
you won't have to go through the same problem of trying again and again to
engage.
I have found that turning the pots may cause a drift which will
show up days later due to the pot being "dirty" or whatever. So what
I usually do is to turn the pot back and forth over several
revolutions so that I can "clean" the contact wiper. I usually make
an initial adjustment and then turn the pot about 1/32 of a turn in
the opposite direction just to relieve any "stress" that might be
there and cause a small change in the output voltage. I usually have very
good results with these methods.
But I will agree with Joe that sometimes it is better just to
leave things alone and just use the known offset from 10 volts when
checking or doing cals.
Bill
----- Original Message -----
From: "Todd Micallef" <tmical...@gmail.com>
To: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
Sent: Thursday, June 12, 2014 7:20 AM
Subject: Re: [volt-nuts] A Fluke 732A: Return it or keep it?
Roy,
The 732A uses the 3059Y-1-101 type cermet pot for the 10V adjustment.
You can use a simple plastic tweaking tool for adjustment. I believe
you will need a fairly long tool. You can shine a light into one of
the other holes to see the orientation of the pot. However, many
people may prefer to
leave
the pot as is and just record the readings. It is going to drift
anyway
and
won't stay adjusted for long. The drift may worsen once the pot
position has changed too. I have adjusted mine, but only after the
broken pots were replaced.
Todd
On Thu, Jun 12, 2014 at 9:57 AM, R.Phillips <phill...@btinternet.com>
wrote:
Hi Joe
Sorry if I am retracing steps, but I have recently had my 3458A
restored/recal'd by Agilent - its good to have it back. I also have
a Fluke 732A which I can now check. Currently it is 10.000024 volts,
I now feel confident to trim it to the 3458A. I have tried to see
the trimmers
in
each of the three holes - they appear to be some way within, and I
am wondering if you could confirm the type of pot. that is used and
just
how
long a trimming device is required. Is this a special tool only
available
from Fluke ?
Regards
Roy Phillips.
-----Original Message----- From: J. L. Trantham
Sent: Saturday, March 08, 2014 10:09 PM
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] A Fluke 732A: Return it or keep it?
Charles,
What size batteries did you use for your external pack and where are
you located? In other words, how long can your external battery
pack
'survive'
keeping the 732A 'hot'? Is the external pack recharged at Fluke or
does
it
have to make a round trip on the initial charge? Once I am
convinced my unit is stable (which will probably be another six
months or so, after I get my 3458A's re-calibrated by Agilent), I
hope to be able to send it to
Fluke
for calibration.
Fluke made a transit case (732A-7002) and a Battery Charger and
Auxiliary
Battery Case (732A-7003). However, I have never seen a picture of
either
of
these. Does anyone have any information on these?
How did you make your case? Did you include a charger? Combination
of battery pack and shipping container or separate battery pack and
shipping
container?
I was thinking of building a case with built-in charger, fuse, and
AC connector and cord such that when the unit arrived at the CAL
facility
all
that would be needed would be to plug it in and allow the external
battery
pack to recharge while the unit being calibrated was plugged in,
recharge
the internal batteries, and calibrated. Or does the 732A also
charge
the
external battery pack along with the internal batteries?
The connector you need (complete with female contacts) is a
Hypertronics P/N D01PB306FSTAH and is in stock at Kensington
Electronics at $8.96 each
(plus
tax and shipping). Only problem is their $50 minimum order.
The 'shell' only is P/N D01PB306NT and the female contact is P/N
YSK006-010ANH (three needed).
http://ecommerce.keiconn.com/hypertronics/D01PB306FSTAH
I ordered two of the connectors from Fluke using a P/N that one of
the Fluke folks in their eCal facility gave me, noting that someone
else had asked the same question a couple of weeks earlier, with
Fluke Item# 2181497, described as '100-166, PLUG - MALE,
HYPERTRONICS'. They were $12.31 each (plus
tax
and shipping) and arrived as the shell only, no contacts.
If Fluke solves their supply chain problem, I sure would like to get
the six female contacts I need to make my connectors 'complete'.
When I got on
the
phone with Fluke, I could never find anyone that had any knowledge
about this. Is there anyone there I should ask for that might
understand my question?
I look forward to your posting the update from Fluke.
Thanks.
Joe
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