Reg T7 low frequency value measure

2 posts / 0 new

Tue, 06/01/2021 - 13:20

Prats

Hi,

I'm having a trouble in reading the low frequency values. I'm having a fucntion geneator conected to FIO0 line of T7. I'm generating a pulse signal with different frequencies using the function generator and reading the frequency from FIO0, with index 3. It is working fine for any frequency > 100hz. But for low frequency values, the freq value changes rapidly and it is not reading the exact value. For eaxmple: For 20Hz freq, it is reading the values between 19 hz to 141hz etc.

Here is my configuration:

DIO_EF_CLOCK0_ENABLE = 1
DIO_EF_CLOCK0_ROLL_VALUE =0
DIO_EF_CLOCK0_OPTIONS =0
DIO_EF_CLOCK0_DIVISOR=1
DIO0_EF_ENABLE =0
DIO0_EF_INDEX =3
DIO0_EF_ENABLE =1
DIO0_EF_OPTIONS =000

Reading : DIO0_EF_READ_A_F
DIO0_EF_READ_B_F

I'm getting the following frequceny values for Freq= 20Hz, Duty cycle=50% and amplitude = 10Vpp.

DIO0_EF_READ_B_F = 69.287827, 28.149172, 68.137703, 19.993227, 20.005102, 81.888910 etc.

For low frequency, values are not accurate and precise. I'm using the kipling software. I have verfied the function geneator signal using the oscilloscaope too. I have tried with Interrupt frequency too and not getting the proper values.

Please let me know if I need to change anything in my configuratior or is there any other way to read the low frequency values?

Tue, 06/01/2021 - 17:20

LabJack Support

First thing to do is remove

First thing to do is remove your signal and instead use the 10 Hz test signal you can get from DAC1:

https://labjack.com/support/software/applications/t-series/kipling/regis...

If that correctly reads about 10 Hz, but your signal is reading higher values, it suggests something is not right with your signal.

Here is one thing we can do to try and spot a problem with your signal.

    1. Add a small jumper wire from DIO0 to AIN0, so both DIO0 and AIN0 are seeing your signal.
    2. Confirm that DIO0_EF still reads wrong with this extra jumper in place.
    3. Use LJStreamM to acquire and log-to-file about 1 second of data from 1 channel (AIN0) at 100 kscans/second.
    4. If you don't spot a problem, post the data so we can check it out.