Observation in 16 samples / sec recording

Bilalalam73

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Jan 3, 2022
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Hi, I'm using ems-220 and trying to observe the response of rpm output with different shift values set for rpm in sfg file. I have set the recording rate to 16 samples / sec to get better insight. However once I check the user log file, I observe that 04 consecutive samples are always same however as per filter design they should change. Is it related to age parameter or by design 04 consecutive samples in 16 samples / sec are same?
 

Bilalalam73

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Jan 3, 2022
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Thanks Airguy. Actually i was doing an experiment in lab in which i simulated RPM sensor output from a function generator and connected to RPM input pin on EMS. Why im doing this experiment. It is because Im trying to select a shift value for RPM measurements which can reduce some spikes in RPM measurements.
Test setup:-
Function generator : Generating square pulses of varying frequency (0-66 Hz), 5Vpk-pk and 50% duty cycle
EMS recording = 16 samples / sec
Shift value in sfg for RPM = 1;
Test waveform: a step input from function generator.
1. t(0) = 0 (0 Hz)
2. t(1) = 790 (around 20 Hz signal)
3. t(3) = 790
.....
1000. t(1000)=790
As per shift description mentioned in the sfg file, the response of RPM measurement should be like :

RPM ={0 395 592.5 691.25 740.625 765.312500000000 777.65 783.82 786.91 788.457031250000 789.22}
where each sample is 62.5 msec apart (1 sec / 16 = 62.5 msec).

However once i checked the user log file, the output was like this:-
RPM ={0 391 391 391 391 590 590 590 590 690 690 690 690 740 740 740 740 765 765 765 765 778 778 778 778 784 784}

My question is:
1. The response is not as per shift description available in the sfg file so there is a possibility that my understanding of shift is not correct.
2. The recording design when samples are set to 16 samples / sec is like this that it repeats the measurement for 04 consecutive samples.

Comments from designers will be very helpful. Im also attaching the user log file for reference.
 

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Dynon

Dynon Staff
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So there's a smidge of undocumented behavior there. The sensor config for RPM is fixed, and doesn't even appear in the sensor.sfg file. If you're playing with sensor file values, you may be playing with the RPM (CAN) sensor config which is for the 912 iS and similar canbus-enabled engines, and is not applicable for this. In any case RPM is updated at 4 Hz, so we would expect to see 4 consecutive identical values.
 
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Bilalalam73

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Jan 3, 2022
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Dear sir / madam, thank you for your reply...
Actually we added a new definition for rpm in the sensor config file therefore the behavior is as expected. We are not changing the RPM (CAN) parameters.

The query was regarding the explanation regarding shift filter given in the sensor config file. As you have informed that rpm is updated at 4 Hz instead of 16 Hz answers my question.
Regards
 
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