Confusion about TLPMX: AvgTime, TimeoutValue and measPower()

[angelotrivelli]

I am using the python wrapper for the TLPMX dll and am having difficulty understanding the usage of the setAvgTime and setTimeoutValue.

The device is a PM103E with a S130VC 1-channel photodiode sensor, and I want to measure the average power of a chopped optical signal (~8KHz). It works fine using the Optical Parameter Monitor application (see screenshot). I am trying to configure a python application to do the same.

The application does not indicate the AvgTime and TimeoutValue for the reading, but I can guess.

parameter, wavelength, bandwidth, and autorange are obvious....

# single channel OPM's use channel = 1
channel = c_uint16(1)  

# Set power units to watts
self.tlpmx.setPowerUnit(c_int16(0), channel)  # 0 = watts

# Set wavelength to whatever is specified
wavelen: float = 633.0
self.tlpmx.setWavelength(c_double(wavelen), channel)

# set to low bandwidth mode LOW
self.tlpmx.setInputFilterState(c_int16(1), channel)  # 1 = low BW

# auto range on
self.tlpmx.setPowerAutoRange(c_int16(1), channel) 

What is not obvious is how to obtain "High Resolution", the only methods I can find are setAvgTime() and setTimeoutValue(). The comments say that timeoutValue
has to be longer than AvgTime, and that AvgTime is rounded to the closest multiple of the device's internal sampling rate. On the application from Thorlabs, the reading changes maybe 5 times a second. So...

# avgTime in seconds, not all values are accepted by the device!
set_avgtime = c_double(0.100)  # 100 ms
self.tlpmx.setAvgTime(set_avgtime, channel)

# timeout is in milliseconds, set to 200 ms
# tlmpmx.py comments require: TimeoutValue > AvgTime
set_tmo_val = c_uint32(200) # 200 ms
self.tlpmx.setTimeoutValue(set_tmo_val)

That seems to work (no exceptions and all return values are 0), but when I try to read the power with this:

channel = c_uint16(1)  # single channel OPM's use channel = 1
power = c_double(0.0)

self.tlpmx.measPower(byref(power), channel)

measPower() raises an exception with the message:

The given session or object reference does not support this operation.

I've tried many permutations of AvgTime and TimeoutValue and I can't get this to work.
Is there something fundamental I am missing?

Thanks!