Re: [volt-nuts] Get 10K resistor calibrated in UK

[John Devereux]

"David C. Partridge"  writes:

> I have recently acquired a Guildline 9330 10K resistor (thank you Phil).
>
> One of my meters says 10,001.251 ohms at a room temperature of about 19.4C
> which is a long way from 2.5ppm or even 12.5ppm (allowing for 5C at 2ppm
> worst case).
>
> Now the question has to be where in the UK (ideally in the Midlands) can I
> get an accurate calibration of this standard resistor at a reasonable cost?
>

Hi David

I used Absolute Calibration UK for my SR104. They charged around £160
and claim an uncertainty of 0.24ppm. They sent a main with a van to
pickup and drop-off, too!

-- 

John Devereux
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Re: [volt-nuts] Time Electronics Ltd 9822

[Stephen Tompsett]

Time were very helpful when I asked about a schematic for an old  1017.


On 06/11/2017 00:52, Illya Tsemenko wrote:
> Hi George,
>
> k
>
>
> On September 18, 2017 7:03:56 AM GMT+08:00, george  
> wrote:
>> Hi all
>>
>> I have a Time Electronics 9822 Multifunction AC-DC Calibrator which has
>> put its feet in to the air.  Does anyone have a schematic or know
>> anything about this unit?  My suspicions are that the power
>> supply/supplies have failed.
>>
>> 73 George G6HIG
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-- 
Stephen Tompsett

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Re: [volt-nuts] Get 10K resistor calibrated in UK

[Tom Knox]

Hi Dave;

I do not think the resistance can be adjusted if that is what you are thinking, 
they will just document the actual value.

But the most important thing is stability.

Cheers;

Thomas Knox




From: volt-nuts  on behalf of David C. Partridge 

Sent: Monday, November 6, 2017 8:43 AM
To: 'Discussion of precise voltage measurement'
Subject: [volt-nuts] Get 10K resistor calibrated in UK

I have recently acquired a Guildline 9330 10K resistor (thank you Phil).

One of my meters says 10,001.251 ohms at a room temperature of about 19.4C
which is a long way from 2.5ppm or even 12.5ppm (allowing for 5C at 2ppm
worst case).

Now the question has to be where in the UK (ideally in the Midlands) can I
get an accurate calibration of this standard resistor at a reasonable cost?

Thanks
Dave


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Re: [volt-nuts] Prema 6048 Cal switch confusion

[David C. Partridge]

I just had an email from Prema about this - - long story short: In this 
particular application, the DS1220AD isn't a good replacement for the DS1220Y 
as the timings differ enough to cause a problem.

Prema suggested to use a ST M48Z02-150PC1, so I've ordered one from CPC.

Dave

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 03 November 2017 17:53
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] Prema 6048 Cal switch confusion

Randy, That's a very good thought.  I think it is OK in this case as the Error 
8 (checksum fail) occurs about 3 seconds after power on.

If necessary,  I think I could replace the MAX691 supervisory chip with one 
that holds the processor in reset for a bit longer (I think the MAX695 would 
probably be a 100% compatible replacement that holds the processor in reset for 
200mS instead of 50mS after Vcc reaches 4.7V  - PLEASE CORRECT me on this if I 
misread the datasheet).

Dave
 
-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Randy Evans
Sent: 03 November 2017 17:17
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Prema 6048 Cal switch confusion

Dave,

Note the following from Maxim AN 202:

I Replaced My Standard SRAM with an NV SRAM and Now My System Doesn't Work at 
All. What Caused This?

In general, this is caused by one of two things:
First, the designer may not have considered the recovery time, or tREC, of the 
particular NV SRAM selected. On power-up, an internal power monitor disables 
the NV SRAM until a power-good situation and then holds it disabled for an 
additional 2ms (max) or 125ms (max), depending on the NV SRAM Page 5 of 9

after power-good. If the microcontroller attempts to access the memory before 
tREC times out, it will not be able to access the device's memory to read or 
write, so the system fails. Either a software loop on power-up to extend the 
access time past tREC, or moving the NV SRAM access somewhere later in the 
power-on initialization sequence in the microcontroller's firmware will resolve 
the problem. This problem often can be corrected by selecting a CPU supervisor 
that has a reset time longer than the recovery time of the NV SRAM.

Second, selecting the voltage levels at which the NV SRAM and the 
microcontroller become active is critical. If the microcontroller becomes 
active below 4.5V, and the NV SRAM becomes active above 4.75V, the same problem 
of the microcontroller trying to access a disabled NV SRAM occurs. The 
power-good threshold for the two devices should force the system to enable the 
NV SRAM first and then the processor. This involves selecting the NV SRAM with 
the appropriate power-good level and pairing that with a CPU supervisor that 
enables the processor at a higher voltage.

Some NV SRAMs have an active-low RESET output that is synchronous with its own 
internal reset. If this is used to reset the microcontroller, the possibility 
of trying to access a disabled NV SRAM is removed.

and:

Are Any NV SRAMs Not Recommended for Future Designs?

Yes. The DS1220Y and DS1225Y are not recommended for new designs. These older 
devices used a battery reference to determine the power-valid trip-point during 
power cycles. Newer designs use a band gap reference. The battery-referenced 
devices had a trip point that decreased during the life of the device. Devices 
using the band gap have a trip point that is stable for the life of the product.

The DS1220AD and DS1225AD are recommended for new designs needing the 
functionality of a 16kb or 64kb NV SRAM. For existing designs, the DS1220AD or 
DS1225AD may be considered as replacements; however, the "Y" parts had a reset 
timeout on the order of milliseconds while the "AD"
parts have a timeout of 125ms. When replacing the Y part with the AD part, it 
must be determined that the controlling processor does not become active during 
a power-up cycle for at least 125ms to ensure that the NV SRAM is available 
before the processor attempts a memory access.

Randy Evans

On Fri, Nov 3, 2017 at 2:54 AM, David C. Partridge < 
david.partri...@perdrix.co.uk> wrote:

> This gets odder and odder.   I put the new DS1220AD into the burner and
> read it.   Pretty random rubbish.
>
> So I cleared it to all FF and inserted into the meter set to Cal mode 
> and powered on - it apparently copied the default Cal constants to the NVRAM.
>
> However when I took it out again and looked at the content it didn't 
> look anything like what I'd read from the original NVRAM, and was 
> mostly still x'FF' but with blocks of ten bytes of zeros at x'100'
> boundaries, followed by zeroes starting at x'6C7' to x'7ef' and what looks 
> like a checksum at
> x'7f0'.   I can't believe that these are cal constants specific to this
> meter!  Though they might be a set of default constants for any 6048!
>
> Filling it with all 00 resulted in an Error 8 (Chec

[volt-nuts] Get 10K resistor calibrated in UK

[David C. Partridge]

I have recently acquired a Guildline 9330 10K resistor (thank you Phil).

One of my meters says 10,001.251 ohms at a room temperature of about 19.4C
which is a long way from 2.5ppm or even 12.5ppm (allowing for 5C at 2ppm
worst case).

Now the question has to be where in the UK (ideally in the Midlands) can I
get an accurate calibration of this standard resistor at a reasonable cost?

Thanks
Dave
 

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