[volt-nuts] 732A and Prologix received
Charles Black
cblack at centurytel.net
Sun Aug 24 22:18:29 EDT 2014
Hi Randy,
You can use the NPLC command to change the A/D converter's'integration
time. Set it to 1000 if you want full resolution. It sets the hp3458a's NMR.
Charlie
On 8/24/2014 6:04 PM, Randy Evans wrote:
> Bill,
>
> I am trying to figure out the MATH function without much success. I input
> the sequence you said (I looked up the instructions to understand what you
> did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG 4;TRIG; and
> it shows up on the display when I input BLUE F1. I hit ENTER and it takes
> the 40 measurements and the MATH symbol shows on the display during the
> measurements. After the SMPL symbol no longer blinks I hit MATH 2 and I
> get a MATH ERR symbol on the display. I tried it a couple of times and the
> same result so I am doing something wrong. Is there a better source for
> explaining how to do front panel masurements than the User Guide, which
> seems oriented at programming automatic rather than manual measurements.
>
> Randy
>
>
>
> On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold <wpgold3637 at att.net> wrote:
>
>> Randy:
>>
>> The MATH function is accessible from the keypad. I don't have an IEEE
>> interface right now that works. You can also program the numeric keypad
>> keys to have preprogrammed functions. DEFKEY
>>
>> I have made my own "low thermal" measurement leads from Pomona #4892
>> banana plugs and Belden #9272 wire. Why 9272, because it was handy at the
>> time. It is tin plated copper, shielded twisted pair 20 ga. I have plans
>> to do custom cables with 16 ga. bare copper wire that I will twist and then
>> put a braided shield over it. I simply cannot find what I want so I will
>> build my own cable. I have done something like this before and it worked
>> fine. When I get a "round toit".
>>
>> I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have
>> used
>> in the past to verify my homemade "low thermal" leads as described above.
>> Frankly I cannot see any difference between using the 1756 cables and my
>> homemade cables once I give them a few minutes for the thermals to go away.
>> As far as I can tell and measure the differences, if any, are below 0.1 ppm
>> at 10 volts.
>>
>> Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all
>> adjustable you may be seeing a misadjusted 1 volt from the 732A. As far as
>> the instability of the readings it is hard to determine which is causing
>> the
>> problem. I have programed (DEFKEY) a numeric keypad key #1 with the
>> following code. "MATH 14;NRDGS 40;TRIG 4;TRIG ;" So what this does is
>> set
>> the MATH to "Statistics" (store high reading/low reading/ and mean of the
>> readings) in the registers, the number of readings to "40", the trigger to
>> "hold" (which keeps the meter from triggering until I press "ENTER" and
>> then
>> trigger the sequence of 40 readings when I push the "ENTER" button. You
>> can
>> do all of this manually from the keypads but since I use this sequence a
>> lot
>> I have preprogrammed it. This is after I set digits to "8" and PLC to 100.
>> Once those 40 readings are finished then you can access the various MATH
>> statistic registers, using the menu, by entering "MATH" and then a 2 for
>> low, a 4 for mean, and 13 for high. Of course you could do all of this
>> through the IEEE also. The 3458A has a very rich set of measurement
>> commands. I am still learning all of them. It depends upon what I am
>> trying to accomplish.
>>
>> Since the 1.018 and 1.0 volt outputs are passive and derived from
>> resistive dividers from the 10 volt, I don't see how they could contribute
>> to the varying readings you are measuring. I think I would put a short on
>> the input of the 3458A and manually set the range to 1 volt and then
>> observe
>> the variations that way without the 732A involved. When I do this I see a
>> variation from low reading to high reading of 0.125 uVolts and then another
>> 40 I get 0.155 uVolts. This is without the GUARD connected to the low side
>> of the measurment terminals, GUARD connected doesn't seem to affect the
>> readings. So that is the base noise of the 3458A without the 732A,
>> somewhere below .2uVolts. When hooked up to the 732A 1.0 volt output I got
>> a variation of 0.159 uVolts using the same 40 reading method above. I
>> would
>> use this to determine where your problem might exist. Just having the
>> meter
>> input shorted will point you in the right direction. Meter, cables or
>> 732A.
>>
>> Sorry for the long dissertation. Friends get mad at me for being so
>> detailed sometimes.
>>
>> Bill
>>
>> ----- Original Message -----
>> From: "Randy Evans" <randyevans2688 at gmail.com>
>> To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
>> Sent: Sunday, August 24, 2014 7:22 AM
>> Subject: Re: [volt-nuts] 732A and Prologix received
>>
>>
>>> Bill,
>>>
>>> I have convinced myself that the problem I an seeing is due to thermals.
>>> If I move the cables (with gold-plated banana plugs) using a small towel
>>> rather than letting my hand touch the plugs, it is much more stable. If
>> I
>>> then hold the banana plug with my hand after the reading has stabilized,
>>> the reading drifts rapidly upward. I am trying to check the stability of
>>> the reading but I haven't figured out the MATH function yet. I assume
>> this
>>> is a programmed function using GPIB only?
>>>
>>> The stability I am seeing by manually recording readings (using NLPC of
>> 100
>>> and 1000) is much greater than what you are measuring on your system.
>> Not
>>> sure how to ascertain if it's the 3458A or the 732. The value of the
>>> readings are very different between the two - the 3458 reads about 50 uV
>>> high on the 10 V output and about 12 uV low on the 1V output. Rather
>> large
>>> differences (this is after an ACAL). I need to find some better cables
>> to
>>> make sure the errors are not due to thermals again.
>>>
>>> Randy
>>>
>>>
>>> On Sat, Aug 23, 2014 at 10:21 AM, Bill Gold <wpgold3637 at att.net> wrote:
>>>
>>>> Randy:
>>>>
>>>> I get 6 volt 4 amp/hr (or 4.5 amp/hr) batteries and they will fit
>>>> perfect. Power Sonic PS-640, Genesis NP4-6, Panasonic LC-R064R5C and
>>>> others
>>>> that are in this size and package. Order from one of the usual
>> electronics
>>>> distributors like Allied, Mouser, Digikey. This is a very common
>> battery
>>>> as
>>>> it is used in a lot of "EXIT" signs so they are lighted when the power
>> goes
>>>> out. I don't see how the 12V 7AH will fit as they are too large. I
>> guess
>>>> you could use a 12V 5AH (PS1250) as it is the same size as 2 x 6 volt 4
>> AH
>>>> but the terminals are in the wrong place so you will have to "nibble"
>> out
>>>> the aluminum plate that holds them in the 732A battery pack. You have
>> to
>>>> be
>>>> careful if you use the 12v 5AH as you will have 4 extra battery
>> connection
>>>> leads to deal with and connect correctly. I would stick with the 6V
>> 4AH.
>>>> New batteries will last around 12 to 14 hours before the "CAL" light
>> goes
>>>> out when AC power is not applied. So shipping to Cal Lab can be a
>> problem
>>>> if it is a distance away, or you have to use a shipper like UPS or
>> FEDEX
>>>> and
>>>> you ship the night before and then use their "Morning delivery" and the
>> Cal
>>>> Lab is expecting your 732A. Same on the way back to you. Of course
>> you
>>>> could always strap another battery on the 732A and hook it up to the
>> "ext
>>>> power" plug to last longer. I have seen it done. The issue is to get
>> the
>>>> Cal Lab to charge the extra battery before they ship the 732A back to
>> you.
>>>> When you remove and work on the battery pack always have the AC
>> power
>>>> plugged in. The "CAL" led will stay on because the 18.6 v regulated
>> supply
>>>> is working.
>>>>
>>>> The "CAL" light is to indicate that power has not been lost to the
>>>> Reference Amp or other associated circuits. When the raw supply
>> (battery)
>>>> voltage drops below about 21 volts the "CAL" light will go out. Below
>> that
>>>> voltage the heater circuits will not work correctly and the 18.6 volt
>>>> regulated supply will not regulate. The requirement is that the
>> Reference
>>>> Amp be kept "alive" at all times to maintain the output voltage that
>> was
>>>> measured at the time of the most recent Calibration or Certification.
>> When
>>>> the semiconductor junctions are unbiased and cool off when power is
>> lost,
>>>> and then power is restored the result will be a different 10 volts than
>>>> before the power failure. My experience is that after all of the years
>>>> that
>>>> these units have been powered up, this won't happen and when power is
>> lost
>>>> and then restored, even months later, the 732A will come back to almost
>>>> exactly the same 10 volts as when they lost power, usually with in 0.2
>> PPM
>>>> after 24 hours of "warm up".
>>>>
>>>> What type of hookup leads are you using when measuring the 1 volt
>>>> output? What is the PLC set to? I always use 100 PLC to measure this.
>> If
>>>> you don't have "low thermal" connection leads you can experience uV
>> changes
>>>> for a minute or more after plugging in the leads due to the "thermals"
>>>> generated because of the difference in temperature between the banana
>> jacks
>>>> on the 732A and the banana plugs of the leads. I have found that even
>> just
>>>> plugging in the lead will generate a thermal difference because of
>>>> difference of temps and some heating due to the physical act of just
>>>> inserting the plug because of friction between the jack and plug (my
>> theory
>>>> at any rate). You have to allow at least a minute or more before being
>>>> able
>>>> to make a measurement after plugging in the leads. I just measured the
>>>> variation of the 1 volt output of my 732A and using my 3458A and I got
>> a
>>>> total difference of 0.159 uV over 40 measurements using 100 PLC on the
>> 1
>>>> volt range of the 3458A. Using the MATH function and all of the data
>> you
>>>> can collect. That was after waiting for several minutes after plugging
>> in
>>>> the leads.
>>>>
>>>> I hope all of this helps.
>>>>
>>>> Bill
>>>>
>>>>
>>>>
>>>> ----- Original Message -----
>>>> From: "Randy Evans" <randyevans2688 at gmail.com>
>>>> To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
>>>> Sent: Friday, August 22, 2014 9:03 PM
>>>> Subject: Re: [volt-nuts] 732A and Prologix received
>>>>
>>>>
>>>>> Todd,
>>>>>
>>>>> Thanks for the info. I have several Panasonic 12V 7 AH batteries
>> that
>> I
>>>>> keep topped off and they have very low current draw (~2 to 3 mA at
>> 13.5
>>>>> VDC) when charged and at their float voltage, so I am pretty sure
>> they
>>>> are
>>>>> in good condition. I will look at getting those in the units after I
>>>>> ascertain the condition of the 732.
>>>>>
>>>>> So now I have a what appears to be a functioning 3458A and a 732A but
>>>> they
>>>>> slightly disagree. I am like the man with two watches that disagree
>> on
>>>> the
>>>>> time - which is correct? For the moment, i am only concerned with
>>>>> stability. The need for absolute accuracy will come later.
>>>>>
>>>>> Randy
>>>>>
>>>>>
>>>>> On Fri, Aug 22, 2014 at 8:06 PM, Todd Micallef <tmicallef at gmail.com>
>>>> wrote:
>>>>>> Randy,
>>>>>>
>>>>>> You have two possible choices. It can be configured with 4 x 6v 4Ah
>>>>>> batteries or 2 x 12v 7Ah batteries. Hopefully the previous owner
>> has
>>>>>> modified the battery pack already. A couple of mine needed a
>> nibbler
>>>> tool
>>>>>> to remove enough of the aluminum cover that fits over the tops of
>> the
>>>>>> batteries. The original cover will short out to the battery tabs
>>>> regardless
>>>>>> of the battery configuration if this is not done.
>>>>>>
>>>>>> You can find larger capacity batteries that will give you slightly
>> more
>>>>>> battery life. I lost a couple sets of mail-order batteries after a
>> few
>>>>>> extended outages. I would recommend going with locally bought
>> batteries
>>>>>> instead of the cheaper mail order. My local Batteries Plus will
>>>> typically
>>>>>> have some warranty if I remember correctly. Moving forward I will
>> only
>>>> use
>>>>>> 2 12v batteries and pre-charge them on a battery charger to
>> equalize
>>>> them
>>>>>> before putting them in the 732A. I think the cheap batteries did
>> not
>>>>>> discharge equally, and would not recover when power was applied.
>>>>>>
>>>>>> Inspect the back plane for damaged traces and look at the
>> capacitors. I
>>>> had
>>>>>> a few that looked questionable. So far, I have replaced all the big
>>>> caps
>>>> on
>>>>>> the pre-regulator and regulator boards. My feeling is that once
>> these
>>>> go
>>>>>> online, they should run as long as possible between repairs.
>>>>>>
>>>>>> The battery charger circuit may need adjusting. I tweaked mine and
>> it
>>>>>> seemed to work fine.
>>>>>>
>>>>>> Todd
>>>>>>
>>>>>>
>>>>>> On Fri, Aug 22, 2014 at 10:42 PM, Randy Evans <
>>>> randyevans2688 at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> I received my Fluke 732A today. Just powered it up but it needs
>> new
>>>>>>> batteries. Any suggestions for sources (I haven't opened up the
>> unit
>>>>>> yet -
>>>>>>> I want to make sure it works before doing that). Also received
>> the
>>>>>>> ProLogix USB-GPIB adapter. I plan on using Mark Sims' CAL ran
>> data
>>>>>> dumper
>>>>>>> program to get the CAL data from my 3458A. Should be a busy
>> weekend.
>>>>>>> Randy
>>>>>>> _______________________________________________
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