WB O2 board pretesting

[bcroe at juno.com]

Here are a few more tests to run before you connect 
your WB sensor to the WB board.  Start with the heater 
test below, and then move on to the servo circuit.

Remove power while changing test setups.

On Sun, 30 Dec 2001 01:17:18 -0600 bcroe at juno.com writes:
> OK, here's a couple ideas on checking the heater circuit.
> 
> Connect a 10 ohm 10 watt resistor and a voltmeter to the
> heater terminals, J1 and J2.  Apply 14 volts to the battery 
> input, + to J3 and J11, - to J4 and J12.  The voltage
> at the heater terminals should rise in a few seconds 
> to between 10.2 and 10.6 volts.  Move the voltmeter to 
> across the 1 ohm 5 watt WB resistor, and the voltage 
> should be around 1 volt.  The heater LED should come on.
> 
> Repeat the tests using a 5 ohm  10 watt resistor.  A 
> pair of 10 ohm in parallel will work.  The voltage across 
> the 5 ohm should be around 6.25 volt, and across the 
> 1 ohm, 1.25 volt.  The LED should not come on.  Do 
> not leave this powered any longer than necessary to 
> make the measurements, or the heater regulator will 
> get very hot.


Connect one end of a 100 ohm resistor to J7.  Connect 
the other end to J5 AND J6.  

The remaining tests may be done with the heater resistor
removed, or with the 10 ohm 10 watt resistor.

J7 should measure 4V  +/- .2V relative to J12 (gnd).  This
checks the voltage regulator and virtual gnd generator
U4A.

After the LED comes on, J6 should measure about .45 V
relative to J7.  This checks the feedback loop including 
U2A, U2B, U2C, the current buffer, and the Vref generator
U4D.  Vout (J8) should measure (with a high impedance 
meter) about 3.84V relative to J12 (gnd).  This checks the 
current sense differential amp U4C and buffer U4B.

With the above setup, apply a short from J9 to J10 
(sensor calibration resistor connections).  J8 should
shift from about 3.84V to about 3.33V relative to J12 (gnd).

Bruce Roe

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