Testing the TK Tar Baby

[poynt99]

.99,

Looks good.  Regarding the 36W figure, how was this arrived at?

Same as before: AVG[V7(t) x V4(t)]

The indicated 182ma would account for around 13 watts.

Sure, sounds about right. I will test the actual battery power and post the result.

ETA: OK, measured the total battery power, and it is +12.5W.

[picowatt]

@.99, PW:

What explains the fact that there is no difference in the current or power calcs?

It would seem to me from inspecting the schematic that there should be less current in the CVR when the FG or other bias source is connected to the common ground. However, in the TB hardware, it also doesn't seem to make much if any difference in scope traces which side of the CVR it's connected to.

TK,

I believe the answer to this is that .99 is using current probes at the indicated locations, and not measuring the voltage across the CSR for current measurements.

PW

[picowatt]

Same as before: AVG[V7(t) x V4(t)]
Sure, sounds about right. I will test the actual battery power and post the result.

ETA: OK, measured the total battery power, and it is +12.5W.

.99,

Are the sim current probes AC and DC, or can you choose one or the other?

PW

[poynt99]

@.99, PW:

What explains the fact that there is no difference in the current or power calcs?

It would seem to me from inspecting the schematic that there should be less current in the CVR when the FG or other bias source is connected to the common ground. However, in the TB hardware, it also doesn't seem to make much if any difference in scope traces which side of the CVR it's connected to.

There is a difference isn't there?

With the FG connected to the high side of the CSR (schema 01 and 03), the battery power is -36W, and current -182mA. With the FG connected to the GND rail (schema02), the battery power is -32W, and current -210mA.

For the power calculations, I am using the two voltages as previously noted, V7, and V4. This is not accounting for the 0.25 Ohm value for the CSR however.

[poynt99]

.99,

Are the sim current probes AC and DC, or can you choose one or the other?

PW

The sim current probes are DC, so they measure 0Hz ~ 10¹⁰⁰ Hz