[Amps] plate voltage meter shunt

[Jim Thomson]

Date: Sun, 04 Nov 2012 09:07:14 -0800
From: Bill Turner <dezrat1242 at yahoo.com>
To: Amps <amps at contesting.com>
Subject: Re: [Amps] plate voltage meter shunt


ORIGINAL MESSAGE: 
On Sun, 4 Nov 2012 07:04:09 -0800, VE7RF wrote:

> I checked all 300 of em..and all 
>300 of em were exactly 200 ohms on the low side..= .2% tol. For an eq resistor,
>the value itself is no big deal, anything from 90-110K is fine. What you want is for
>them to all be the same. 

REPLY: 
You got lucky on that batch and here's why. 

When manufacturers make resistors,they make a huge batch of them. They then
cherry pick out the tightest tolerance ones and sell them at a premium price.
Then they next cherry pick out the next lower tolerance and sell at a lower
price. Then they cherry pick out the next lower yet tolerance, etc, etc. 

This means that the second and third cherry picking gets both ABOVE and BELOW
the tighter tolerance units. You were lucky to get all of yours on the low side,
but next time they could have been mixed high and low or all high.

The point is you must still individually check each resistor if you want to be
sure they are matched.

73, Bill W6WRT

### There is 100 in a box.  I bought 3 box’s  of em.  Each box was from a DIFFERENT  lot number. 
I bought a 4th box, several  years later, and it too ends up with the same results. 

##  In theory, the worse case for any 1% tol rated resistor’s  would be that some are 1% on the high
side, and some are 1% on the low side = a 2% max spread between extremes.  In actual practice, 
for whatever reason, that never happens.  In talking to other folks who have bought the same Vishay
1% tol resistors in 100k format, they too measured the same results.  

##  The late Tony King, W4ZT, put me onto these Vishay brand 1% , 3 watt mof’s.   He was getting fed up with
the slow, tedious process of having to go through the rigmarole of 1st  measuring +  labeling 100 individual   5% tolerance 
resistors. Then having to enter 100 measured values into a spreadsheet,  just to sort em out for various applications.
IE: one supply requires 8 x eq resistors, and the next one requires 12 etc.  

##  With these Vishay 1%  tol resistors, it’s just grab how many you need.... (then measure em just to be sure) .
Either Vishay has come up with the best thing since sliced bread, or 8 of us have been extremely lucky over the last
6 years.   Don’t believe me, buy a box, and see for yourself. 

### 100k 3 watt MOF EQ, 1% TOL resistor’s. 
VISHAY, CPF3100K00FHB14 

## Vishay Cust pn # 71-CPF3-F-100K-T2.... available from Mouser, 100 per box. 

Later... Jim   VE7RF