Lightbulbs make great AC loads, but use a line filter in series with them
and you'll probably duplicate most EUT's since they'll be using filters.
- Robert -
On Fri, 9 Oct 1998 [email protected] wrote:
> Hi Ed,
>
> I appreciate your kindness to share your experience with us about
> constructing equivalent load: "I constructed a load bank consisting of 16
> surface mount light bulb sockets, all wired in parallel. I just screw in an
> array of 25/60/75/100 Watt rated lamps until I get the necessary current.
> Sure, there's some unknown slight lead inductance and capacitance. But all
> I want to do is draw a few amps DC"
>
> I have two questions: (1)What is the impedance of your bulb array at 30
> MHz? i.e., Zb=? @30 MHz. (2)What is the impedance of EUT at 30 MHz?
> i.e., Ze=? @30 MHz
>
> If we are not sure Zb=Ze @30 MHz, I am afraid, it's hard to say the
> spectrum analyzer would receive the same RF emission at 30 MHz from noise
> sources other than EUT, although the bulb array draws the same current at
> 60 Hz as EUT does. In other words, Zb=Ze @60 Hz is one thing, and Zb=Ze
> @30 MHz would be another.
>
> Let's see an example, assuming
> Ze=Re+jXe, where Xe=Omega*Le, and Omega=2*Pi*F.
> Re=20 Ohm, Xe=0.1 Ohm @60 Hz, Ze=20+j*0.1=>20 Ohm
> Be=20 Ohm, Xe=50000 Ohm @30 MHz, Ze=>j*50000 Ohm
>
> Conclusion: As far as the equivalent load is concerned, we can only pay
> attention to the equivalence of resistance part of Zb and Ze @60 Hz. At 30
> MHz, however, we should pay more attention to the equivalence of reactance
> part of Ze and Zb instead.
>
> Suggestion: We might need to check the equivalence of Zb and Ze @30 MHz by
> using an Impedance Analyzer, e. g., HP4191A(?).
>
>
> Thank you.
> Please correct me.
> Best Regards,
> Barry Ma
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