Electronics > Metrology

Leeds & Northrup 4737-A20 tear down

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r6502:
Hello all,

in the mean time the L & N 4737-A20 Guarded Wheatstone Bridge has arrived.

I did not power it up, but I opened it, to take some photos, see below:

Frontpanel:


Rear Panel:


Inside view, whole device:


Front terminals:


Front small switches:


Resistors on range selector and 1st stage:


Resistors on stage 5:


Resistors on stage 6:


Housing, heavy aluminum die cast:


Hafe fun to look at details - Guido




vindoline:
Beautiful. Thank you for the pictures!

Vgkid:
Thanks for the teardown. Interesting that the lowest decade is 0.01 Ohms. I figured that it would have been 0.1ohms like the 4232. It looks like your unit is newer than mine. Cool to see those smaller super accurate resistors.

trobbins:
Interesting that the lowest decade is a continuous wire.  I presume each segment was adjusted down by filing, with no way to add resistance back in, and then the assembly was enamelled.

Kleinstein:
The vey lowest resistor part does not have to be that accurate - some +-10% may be acceptable there. No trim needed, just get a reasonable good length of the wire.
The tricky part is more with the switches, to get a stable and low constact resistance.

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