Fluke resistor codes

[gbaddeley]

Hi,
Does anyone have information about codes found on Fluke precision resistors, particularly in Fluke test equipment?
eg. FL4P2 FL2P1 FL2P2 FL1N4 that I have seen on green tubular resistors and mica card wire wound resistors.
Glenn

[doktor pyta]

I measured tempco of two green Fluke resistors:

one with marking 'P1' has approx. +1ppm/'C @30'C
one with marking 'P0.5' has approx. +0.5ppm/'C @30'C

(https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg1209379/#msg1209379)

But Your codes don't use comma.
So it might be similar to Zener diodes marking (5V1= 5.1V)

To make sure, please write if all these resistors have same size.

[gbaddeley]

Tonight I found https://xdevs.com/article/f720a_res/
I think P and N mean positive and negative tempco.
There are examples of designations after this letter being 0.5, 1, 1.5, 2, 3, 4
This is almost certainly PPM / deg.C

The 8375A DVM (1970's vintage) has R5 and R6 in series in the input divider network.
They are both 4.45 M ohm, one is GL1P4 and the other is GL1N4, giving a net tempco of zero !

Newer resistors seemed to be marked directly with tolerance +/-0.02% +/-0.01% etc
and don't have any codes like FL1 FL2 FL4 etc.
I think these are older Fluke internal codes that represent the construction / power / tolerance.

The first letters of codes I have encountered so far are:
E = Small tubular and mica former, approx 0.5 - 1W rating (?)
F = Medium mica former, approx 1 - 2W
G = Big tubular, approx 2 - 5W

Second letter and first digit:
H1, H2, H3, H4
L1, L2, L3, L5, L6
I suspect these relate to the tolerance, and are all below 1%.

[gbaddeley]

Regarding second letter and first digit, I have only encountered H or L so far.
Could this mean High and Low, like P and N mean Positive and Negative?
I am fairly sure that L1 = +/- 0.02%.
I have parts from an 887AB Differential Volt Meter, 4999.1 and 2499 ohms marked FL1 and they correspond to +/- 0.02% in the manual's parts list.
Are there any Fluke gurus out there that can offer an opinion?