[Collins] Meter sensitivity-312B-4 etc

[Dave Brown]

Looks like the consensus is 200uA. I might just pull out one of the 
312B-4s tonight and measure it directly, although I'm pretty convinced 
now that I'll see 200 uA.
 The cct of the 312B-4 in the yellow book (forgot about that!) is as 
per the parts list in the handbook for the 312B-4 - no meter 
sensitivity mentioned. But the 302C-1 cct, a page or two further on, 
(100w and 1 kw, not 200w and 2 kW as for the 312B-4) shows that 290 uA 
beside the meter. The ccts are of course identical-apart from the cal 
resistors which are AOT.
Interestingly-I rememberd I had a standalone directional wattmeter, 
the mil version of the 302C-3, so I found that and it has the movement 
sensitivity (200 uA) written on the bottom of the scale. But the meter 
movements in the 312B-4s have no markings in the corresponding 
location.
And the meter in the 302E-2 (in the 32RS-1) is 200 uA as 
well-according to the circuit. The rest of the cct is again identical 
to the others, apart from the diode DC return resistors which are 21.5 
ohms, as opposed to 10 ohms in the later versions.
 This all started because I want to use a pair of identical meters (a 
JRC cross needle dual 100 uA meter in fact) driven from one of the 
Collins couplers for a temporary test setup-hence the need to find out 
what meter sensitivity was needed. Thanks anyway, Bill!
73
 Dave, ZL3FJ


----- Original Message ----- 
From: "Gerald" <geraldj at ispwest.com>
To: "Mac McCullough" <w5mc at austin.rr.com>
Cc: "Dave Brown" <tractorb at ihug.co.nz>; <collins at mailman.qth.net>
Sent: Tuesday, April 19, 2005 9:57 AM
Subject: Re: [Collins] Meter sensitivity-312B-4 etc


> On Mon, 2005-04-18 at 16:01 -0500, Mac McCullough wrote:
>> all the older Simpson style had it marked down in the corner of the 
>> scale,
>> later bartlet ones did and didn't , but they were still 200ua 
>> movements..
>> mac/mc
>>
> I've marked my schematic in red ink.
>
> -- 
> 73, Jerry, K0CQ, Technical Advisor to the CRA
> All content copyright Dr. Gerald N. Johnson, electrical engineer
>
>
>
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