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ADC-20 can't keep time

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ADC-20 can't keep time

Postby chriscatford » Tue Mar 16, 2010 8:18 pm

Hi,
I'm using the ADC-20 to record readings every second, but the actual sampling rate is much slower than one second; for every ten seconds of real time, I get about eight samples.
Any clues?
Thanks in advance, Chris
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Re: ADC-20 can't keep time

Postby PeterF » Wed Mar 17, 2010 9:19 am

Hi,
To look at this, I will need details of the PC hardware you are using, version of Windows and version of PicoLog. If possible, send a settings file or short data file to support@picotech.com as well.
Regards,
PeterF.
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Re: ADC-20 can't keep time

Postby chriscatford » Thu Mar 18, 2010 10:09 am

Hi Peter,
Thanks for you answer.
The details of the system are as follows;
Asus EEEpc 901 with an Atom 1.6 CPU, 1Gb Ram, running Windows XP service pack 3 and picolog 5.20.1
I'll send a data file to the support email address.
Regards, Chris
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Re: ADC-20 can't keep time

Postby PeterF » Thu Mar 18, 2010 1:43 pm

Hi Chris,
Could this be the problem?
From another customer with the same PC:-
"Seems like the software is dependant on the CPU frequency, the EeePC goes into power-saving mode while on battery.
After disabling the lowering of CPU frequency the timings are spot on!"
Regards,
PeterF.
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Re: ADC-20 can't keep time

Postby chriscatford » Thu Mar 18, 2010 4:25 pm

Peter, that's the answer. I tested it with the pc on the mains and it can now tell the time. Is this something Pico can fix in the software? There must be plenty of uses for data loggers when there's no mains around, and max battery life is required.

Thanks for you help though, and regards
Chris
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Re: ADC-20 can't keep time

Postby PeterF » Fri Mar 19, 2010 8:16 am

Hi Chris,
The lowering of clock speed on battery power is a PC function, not PicoLog. I understand that you can inhibit that function in the PC settings.
Regards,
PeterF.
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Re: ADC-20 can't keep time

Postby chriscatford » Fri Mar 19, 2010 10:21 am

Peter,
What I meant was why is picolog's timing reliant on the cpu clock? The pc's own clock isn't effected by the cpu speed for example.
Rgds, Chris
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Re: ADC-20 can't keep time

Postby PeterF » Fri Mar 19, 2010 11:51 am

Hi Chris,
The PC has a real time clock unaffected by clock speed and the hardware also knows when the clock speed changes and can compensate other timings on the PC.
We have no way of knowing when the clock speed changes, so that will affect our timing.
Regards,
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Re: ADC-20 can't keep time

Postby chriscatford » Fri Mar 19, 2010 9:29 pm

OK Peter, I give in. I guess I don't know enough about software and how computers work. I just thought (naively obviously) that as it's quite common for pc's to slow down when running on batteries, there'd be a way to deal with it. Oh well.
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