[ARC5] RE meters

[Rev. Don Sanders]

Anyone have a thermocouple I can use with the meter I have?

Healthfully yours,
                          DON
----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: "philip" <signetics at netzero.com>
Cc: <ARC5 at mailman.qth.net>
Sent: Monday, April 18, 2005 4:25 PM
Subject: Re: [ARC5] RE meters


> That's not a surprise. The meter is actually linear, but the scale is
calibrated
> to correct for the non-linearity in the current sensor.
>
> The thermocouple unit has a series resistor in the RF circuit (The current
> transformer just isolates and scales.. it is linear). The power dissipated
in
> the R of the sensor is current squared x R  (I**2 x R) and is non.linear.
> Assuming the heat losses in the thermocouple assembly are by conduction
only
> (good approximation) the temperature rise will be proportional to the
power
> dissipated, or the square of the RF current. The thermocouple produces a
voltage
> proportional to temperature, and so is linear.
>
> So, in short, the non-linearity is due to the heating effect of the RF
current,
> which is proportional to the current squared. The scale corrects for this.
>
> -John
>
> philip wrote:
>
> > One thing I do know about the antenna relay meter is that
> > it is nonlinear. The meter movement that is.
>
>
>
> _______________________________________________
> ARC5 mailing list
> ARC5 at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/arc5
>