Altitude encoder anomaly

Andy,

A question about the current draw. Eric measured the A-30 current a
few years back and reported a maximum draw of up to 0.4 amps, as you
also got. But Eric found that once things stabilized, the current draw
dropped to 0.090 amps. Your measurements seem to show a heater off
current minimum of 0.200 amps, more than twice what Eric found.

Do you think this 2x current draw is more because your A-30 is
malfunctioning, or do you think this might point to variability in the
A-30 manufacturing?

-John

On Dec 27, 2:17 pm, Andy wrote:
For the bench test the encoder was
cold soaked overnight in the freezer at approx +5 deg F. It was then
powered and the current draw and altitude code were monitored.

Time zero current 0.37 A. No altitude report.
4 minutes 0.40 A. No altitude report.
10 minutes 0.35 A. No altitude report.
11 minutes 0.30 A. 22,100 ft.

After about 13 minutes the current stabilized between 0.24A and 0.26A
and the reported altitude continued to reduce. (Current includes
monitor LED current so varies with altitude)

[ In a later post on Dec 27, 4:25 pm, Andy wrote: ]

BTW additional current measurements with monitor LEDs out of circuit
showed post warm up current of 0.15A with strobe open and 0.20 with
strobe enabled. Bench power supply set to 12v.

On Dec 28, 7:44*am, jcarlyle wrote:

Do you think this 2x current draw is more because your A-30 is
malfunctioning, or do you think this might point to variability in the
A-30 manufacturing?

Sorry I don't know the answer to that. I was surprised the stobe
enabled current was so much higher that the disabled current for an
unterminated unit. Perhaps there is switched power to the line
drivers. Mine is a Mod 1 unit. On-line pictures show the case is
different at the static port so there may be a substantial redesign
between mod 1 and mod 4 units.

Andy