Fluke 742 resistor hardware clone ? any interest ?

[Overspeed]

Hello

I plan to manufacture CNC enclosure base on the 742 design so :

Main enclosure
Lead enclosure drilled for 4 mm post ( will be designed to allow opening to BNC )
Foam insulation
Copper blade
Internal blades support in Perplex / PEHD1000 ??
S304 screws set

let me know your feed back

Regards
OS

[Dr. Frank]

That's interesting.
I suggest to add a precision temperature sensor, and a feature to thermally couple the resistors, because that is a design flaw of the Fluke 742A, and the WEKOMM RS9010A, compared to the SR104.

[Overspeed]

That's interesting.
I suggest to add a precision temperature sensor, and a feature to thermally couple the resistors, because that is a design flaw of the Fluke 742A, and the WEKOMM RS9010A, compared to the SR104.

Hello

Yes I have planed to install a Pt100 sensor well through the front panel

Regards
OS

[maat]

Are you interested in open source the design files?

If so, I would be interested in manufactured units as well.

[Overspeed]

Hello

Yes perhaps asap I have supply my own need and make some tests , take in considerations that request CNC machining or at least time and manual milling machine , as all ''electronic guys '' have this equipment.

I use slice cut of square 100 mm x 100 mm 6061 extruded tube to avoid machining from a block of light alloy and keep the price low as possible

That a front and back lead enclosure so that allow to pour the enclosure with insulation balls if needed or even to use the enclosure both faces to avoid the need of two enclosures for two different refs as 10 K and 100 K for example .

Regards
OS

[MiDi]

Alternative to manufacture from scratch e.g. https://de.aliexpress.com/item/32884407649.html

[Mickle T.]

When I made the Fluke 742 clone, I used a silumin Gainta electrical enclosure with a thermally and electrically insulated inner copper case.

[Overspeed]

Alternative to manufacture from scratch e.g. https://de.aliexpress.com/item/32884407649.html

Hello

Yes but that thin aluminium and also not really easy to install the copper rails , can be a solution for simple foil resistor , I need to use parallel resistors with robust  setup .

Regards
OS

[Overspeed]

When I made the Fluke 742 clone, I used a silumin Gainta electrical enclosure with a thermally and electrically insulated inner copper case.

Hello

Nice setup , I like the ceramic castle slotted rest with the copper link

I have some extruded square tube in aluminium I have designed lead look a like Fluke 742 with a temperature well made in a SS304 bolt blind drilled , to keep the price low as  possible .

Regards
OS

[laichh]

There are some pretty decent off-the-shelf aluminum enclosure to choose from. Personally I would go for ROSE Enclosure Aluform series 040808080 (80*80*81 mm), or 041212080 (120*120*81 mm) if the size does matter.

https://www.rose-systemtechnik.com/en/rose-products/040808080/

https://www.rose-systemtechnik.com/en/rose-products/041212080/

[aronake]

Someone in China has allready made "Fluke 742 inspired" boxes and sell these.



One way forward could be that instead of making something that look like a 742 box, critically think (and maybe experiment) how a box can be made better. Good arrangements for thermal coupling and temperature measurements as mentioned here. Good arrangements for mounting or soldering resistors. Maybe some thermal insulation.

[Overspeed]

Someone in China has allready made "Fluke 742 inspired" boxes and sell these.

(Attachment Link)

One way forward could be that instead of making something that look like a 742 box, critically think (and maybe experiment) how a box can be made better. Good arrangements for thermal coupling and temperature measurements as mentioned here. Good arrangements for mounting or soldering resistors. Maybe some thermal insulation.

Hello

Impressive including the front label .... Question : do you know the price as my Chinese speaking and reading is quite poor

Regarding how the box can be good yes , as that possible to include shielding ( double metal skin outside in aluminium alloy internal in copper nickel plated or even steel nickel plated ? ) and thermal insulation and a temp sensor well

See Zlymex DIY resistor box  https://www.eevblog.com/forum/metrology/teardown-standard-resistors/25/

Regards
OS

[laichh]

My approach, the enclosure is Hammond R196-082-000, the two side plastic covers were broken by accident.

[aronake]

Someone in China has allready made "Fluke 742 inspired" boxes and sell these.

(Attachment Link)

One way forward could be that instead of making something that look like a 742 box, critically think (and maybe experiment) how a box can be made better. Good arrangements for thermal coupling and temperature measurements as mentioned here. Good arrangements for mounting or soldering resistors. Maybe some thermal insulation.

Hello

Impressive including the front label .... Question : do you know the price as my Chinese speaking and reading is quite poor

Regarding how the box can be good yes , as that possible to include shielding ( double metal skin outside in aluminium alloy internal in copper nickel plated or even steel nickel plated ? ) and thermal insulation and a temp sensor well

See Zlymex DIY resistor box  https://www.eevblog.com/forum/metrology/teardown-standard-resistors/25/

Regards
OS

This is from a Chinese app called Xianyu. Main purpose of the app is for private people to sell used things. Seems there are some volt-nuts selling all sorts of interesting things there as well. It seems to me that a chinese phonenumber is needed to register as a user, and I have not figured out how to sort that out yet.

[zrq]

Someone in China has allready made "Fluke 742 inspired" boxes and sell these.

(Attachment Link)

One way forward could be that instead of making something that look like a 742 box, critically think (and maybe experiment) how a box can be made better. Good arrangements for thermal coupling and temperature measurements as mentioned here. Good arrangements for mounting or soldering resistors. Maybe some thermal insulation.

Hello

Impressive including the front label .... Question : do you know the price as my Chinese speaking and reading is quite poor

Regarding how the box can be good yes , as that possible to include shielding ( double metal skin outside in aluminium alloy internal in copper nickel plated or even steel nickel plated ? ) and thermal insulation and a temp sensor well

See Zlymex DIY resistor box  https://www.eevblog.com/forum/metrology/teardown-standard-resistors/25/

Regards
OS

Just checked that out in Xianyu, the price is 5555 CNY and the seller said lower offers are not considered. Probably not worth it.

[shenxiaoming]

5555 cny contains four Fluke resistors.

[shenxiaoming]

The inside of the 742 shell is the same.
I copied the 732 shell and datron4910, and installed the 4910 single-channel cell1, with adr1000 as the benchmark.、
6581 Test 732C(adr1000)10V for one night.

[ddrl46]

How did you make those front panel labels? Did you make them yourself or have them manufactured?

[Overspeed]

Hello

No , front panel label can be ordered bespoke made from sticker companies if you send the CAD file , price is very reasonable if you order per 10 or more

Printer have cutter so they can cut hole all around the posts

Regards
OS

[shenxiaoming]

Draw your own drawings, and then go to Taobao for customization, which is very cheap.

[Overspeed]

Hello

A screen print of my 742 enclosure , as I have 150x150 mm 6082 tube I have designed twin resistor value enclosure to group 0.1 and 1 Ohm or use two same value side by side one very low tempco and one other ''general purpose'' a lower cost or with higher current value

There is one central temp sensor well .

the box is set to add four post in a raw to use the the resistors as divider

front milled pockets are made to install stickers not flush so protected

Internal is a clone a the Fluke 724 with PTFE support on aluminium plate , perhaps SS304 as I want to avoid aluminium conversion surface treatment as alodine to keep price low.

Regards
OS
 

[Overspeed]

Hello

Progress . the rear lid

I plan to use polystyrene ball as insulation

Regards
OS

[mendip_discovery]

does that not cause static electricity?

[Overspeed]

does that not cause static electricity?

Hello

yes ,but antistatic polystyrene exist

https://productpackagingsupplies.com/Category/Anti-Static-Polystyrene-Packing-Peanuts

other method is to increase thermal inertia by using block of metal all around the resistors . zlymex on this forum have a different assessment I link a screen-print

Regards
OS

[Overspeed]

Hello

As technical solution I go with a clone of IET solution ,that allow a wide range of setup and drilling is easy even with a hand drill.

I link two pictures from Zlymex forum member

Regards
OS