On 21/01/2018 18:27, Bob Albert via volt-nuts wrote:

you possibly need to be logged into eevblog at the same time as you follow the link?

OK folks here's another location for anyone who can't get it from eevblog.com:

http://www.perdrix.co.uk/manuals/Fluke%20732A%20Reference%20Circuit.pdf

Dave

-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces+david.partridge=perdrix.co.uk@febo.com] On Behalf Of m k
Sent: 21 January 2018 22:29
To: Bob Albert; Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Redrafted schematic of Fluke 732A reference circuit

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David,
Thank you for that - much easier to follow. I infer from this that you have a Spice model for the LTFLU. Can you elaborate, please?
Roman

It's nothing fancy just a glom of a 2n3904 and a 6.2V Zener wrapped up in .subckt/.ends and makes no claim to a an accurate model (I somehow doubt that either Fluke or LT would be willing to share that).

** LTFLU **
*

• NI Multisim to SPICE Netlist Export
• Generated by: amonra
• Sat, Jan 20, 2018 15:16:41

.SUBCKT LTFLU C B EK A

## Multisim Component LFLUD1 ##
xLFLUD1 A EK BZX84B6V2LT1/ON__ZENER__1

## Multisim Component LFLUQ1 ##
qLFLUQ1 C B EK 2N3904__BJT_NPN__1

.SUBCKT BZX84B6V2LT1/ON__ZENER__1 2 1

•  Model Generated by MODPEX     *
  

Copyright(c) Symmetry Design Systems

•     All Rights Reserved        *
  

• UNPUBLISHED LICENSED SOFTWARE  *
• Contains Proprietary Information *

•  Which is The Property of      *
  

• SYMMETRY OR ITS LICENSORS      *
  

*Commercial Use or Resale Restricted *

• by Symmetry License Agreement    *

• Model generated on Dec 11, 03
• MODEL FORMAT: PSpice

• anode cathode
  

*node: 2      1

• Forward Section
  D1 2 1 MD1
  .MODEL MD1 D IS=5.21532e-16 N=1 XTI=1 RS=0.5

• CJO=9.5e-11 TT=1e-08

• Leakage Current
  R 1 2 MDR 2e+07
  .MODEL MDR RES TC1=0 TC2=0
• Breakdown
  IZG 4 2 0.12
  R4 4 2 300
  D3 2 4 MD3
  .MODEL MD3 D IS=2.5e-12 N=0.37046 XTI=0 EG=0.1
  D2 5 4 MD2
  .MODEL MD2 D IS=2.5e-12 N=1.16158 XTI=0 EG=0.1
  EV1 1 5 6 0 1
  IBV 0 6 0.001
  RBV 6 0 MDRBV 5792.79
  .MODEL MDRBV RES TC1=0.000353198
  *-- PSpice DIODE MODEL DEFAULT PARAMETER
• VALUES ARE ASSUMED
  *IS=1E-14 RS=0 N=1 TT=0 CJO=0
  *VJ=1 M=0.5 EG=1.11 XTI=3 FC=0.5
  *KF=0 AF=1 BV=inf IBV=1e-3 TNOM=27
  .ENDS bzx84b6v2lt1

.MODEL 2N3904__BJT_NPN__1  NPN(Is=6.734f Xti=3 Eg=1.11 Vaf=74.03 Bf=416.4 Ne=1.259

•           Ise=6.734f Ikf=66.78m Xtb=1.5 Br=.7371 Nc=2 Isc=0 Ikr=0 Rc=1
  

•           Cjc=3.638p Mjc=.3085 Vjc=.75 Fc=.5 Cje=4.493p Mje=.2593 Vje=.75
  

•           Tr=239.5n Tf=301.2p Itf=.4 Vtf=4 Xtf=2 Rb=10)
  

.ENDS LTFLU

-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of romeo987
Sent: 23 January 2018 10:31
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Redrafted schematic of Fluke 732A reference circuit

David,
Thank you for that - much easier to follow. I infer from this that you have a Spice model for the LTFLU. Can you elaborate, please?
Roman

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and follow the instructions there.

I tried that some time ago but, not surprisingly, the model didn't behave quite the same as the real thing in the lab. I concluded )to myself, only!) that chip self-heating and thermal coupling between the two devices was the stumbling block. Then after I sent the question to you yesterday, I did a bit of idle googling and came across this
bbs.38hot.net/thread-105042-1-1.html
(Not sure if the url pasted correctly...here are the salient bits

"Hello fellow forum users,

I just finished with a telephone conversation with Bob Dobkin, and he was short on time, so I was not able to get all of the answers to every question I [and we] had, but here are the ones I was able to get:
....
....
5) They could make a model for LTspice, but the temperature effects are very difficult to simulate, and the market need is not large enough to support the development effort [my words].  He said the best way is to build the circuit and test it out in real life.
,,,"

Anyway, good job.  I don't have a 732A, but am looking to get more than I paid for out of a 332B which happens to have had its RefAmp replaced with an LTFLU (before I got it). I am looking at your circuit now as food for a bit of improvement, perhaps...
Roman

-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of David C. Partridge
Sent: Tuesday, 23 January 2018 10:03 PM
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] Redrafted schematic of Fluke 732A reference circuit

It's nothing fancy just a glom of a 2n3904 and a 6.2V Zener wrapped up in .subckt/.ends and makes no claim to a an accurate model (I somehow doubt that either Fluke or LT would be willing to share that).

** LTFLU **
*

• NI Multisim to SPICE Netlist Export
• Generated by: amonra
• Sat, Jan 20, 2018 15:16:41

.SUBCKT LTFLU C B EK A

## Multisim Component LFLUD1 ##
xLFLUD1 A EK BZX84B6V2LT1/ON__ZENER__1

## Multisim Component LFLUQ1 ##
qLFLUQ1 C B EK 2N3904__BJT_NPN__1

.SUBCKT BZX84B6V2LT1/ON__ZENER__1 2 1

•  Model Generated by MODPEX     *
  

Copyright(c) Symmetry Design Systems

•     All Rights Reserved        *
  

• UNPUBLISHED LICENSED SOFTWARE  *
• Contains Proprietary Information *

•  Which is The Property of      *
  

• SYMMETRY OR ITS LICENSORS      *
  

*Commercial Use or Resale Restricted *

• by Symmetry License Agreement    *

• Model generated on Dec 11, 03
• MODEL FORMAT: PSpice

• anode cathode
  

*node: 2      1

• Forward Section
  D1 2 1 MD1
  .MODEL MD1 D IS=5.21532e-16 N=1 XTI=1 RS=0.5

• CJO=9.5e-11 TT=1e-08

• Leakage Current
  R 1 2 MDR 2e+07
  .MODEL MDR RES TC1=0 TC2=0
• Breakdown
  IZG 4 2 0.12
  R4 4 2 300
  D3 2 4 MD3
  .MODEL MD3 D IS=2.5e-12 N=0.37046 XTI=0 EG=0.1
  D2 5 4 MD2
  .MODEL MD2 D IS=2.5e-12 N=1.16158 XTI=0 EG=0.1
  EV1 1 5 6 0 1
  IBV 0 6 0.001
  RBV 6 0 MDRBV 5792.79
  .MODEL MDRBV RES TC1=0.000353198
  *-- PSpice DIODE MODEL DEFAULT PARAMETER
• VALUES ARE ASSUMED
  *IS=1E-14 RS=0 N=1 TT=0 CJO=0
  *VJ=1 M=0.5 EG=1.11 XTI=3 FC=0.5
  *KF=0 AF=1 BV=inf IBV=1e-3 TNOM=27
  .ENDS bzx84b6v2lt1

.MODEL 2N3904__BJT_NPN__1  NPN(Is=6.734f Xti=3 Eg=1.11 Vaf=74.03 Bf=416.4 Ne=1.259

•           Ise=6.734f Ikf=66.78m Xtb=1.5 Br=.7371 Nc=2 Isc=0 Ikr=0 Rc=1
  

•           Cjc=3.638p Mjc=.3085 Vjc=.75 Fc=.5 Cje=4.493p Mje=.2593 Vje=.75
  

•           Tr=239.5n Tf=301.2p Itf=.4 Vtf=4 Xtf=2 Rb=10)
  

.ENDS LTFLU

-----Original Message-----
From: volt-nuts [mailto:volt-nuts-bounces@febo.com] On Behalf Of romeo987
Sent: 23 January 2018 10:31
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Redrafted schematic of Fluke 732A reference circuit

David,
Thank you for that - much easier to follow. I infer from this that you have a Spice model for the LTFLU. Can you elaborate, please?
Roman

volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.