Scan Rate Error

[Nils]

Hello, new to DASYLab and have som issues.

When I set up two different modules I get error of max software scan rate of 500 or too little samples.

Is this a limit of:

a) HW from MCC

b) Software settings I made

c) PC

 

HW: MCC USB-1208HS-4AO with sampling rate up to 1 MS/s.

SW: DASYLab 2022 Basic

PC: Intel(R) Core(TM) i5-6200U CPU @ 2.30GHz, 8 GB ram, Win 10.

 

 

Ai_to_Do.DSB

[JRys]

Hello,

The 16-bit port on the USB-1208HS-4AO does not have the high-speed scanning circuitry found on the analog input and output channels. Because of this, it is slow, usually less than 100 Hz, depending on the number of output lines. The module that proceeds the digital output will dictate the output speed. You should use the DASYLab time base for the analog input. Press the Measurement button on its setup dialog to change the time base. 

The analog output can be fussy. Depending on the update rate, it will want block sizes that can be pretty large. The output's time base, rate, and block size must match the analog input. Try the following: Set the analog input time base to USB-1208HS-4AO Device1 - Input HW. Set the rate to 1000 Hz with a block size of 5000. Set the analog output time base to USB-1208HS-4AO Device1 - Output HW. Set the rate to 1000 Hz with a block size of 5000. You will see a lag between the input and the output; it won't be simultaneous.

Because there is one analog input time base, if you configure it for analog output, your digital output will generate an error. A way around this issue is to write the analog input value to a global variable. Then use a global variable read module to send the value to the digital output. This separation will allow the analog input to run faster while maintaining the slow speed required by the digital output. 

If this is your first day with DASYLab, you unknowingly stepped into one of the more difficult DASYLab topics: time bases. 

Best regards,
John

[Nils]

Thank you! Now I understand more. Found some limits of  simple configs.

With analog input connected to Y/t chart I need to use HW time base to get over max scan rate of 500.

With a switch connected to analog output I need HW time base to get 10 kHz sample.

Is HW time base preferred before DASYLab time base when working with high frequencies?

Nice to write input value to global variable. Is the scan or R/W speed to global variables over 10 kHz?

 

Thank you

Nils

[JRys]

The HW time base uses the USB-1208HS-4AO internal scanning circuitry to collect data at high speeds. DASYLab and the SW time base are executed in a software loop, so their rate is limited.

I don't know how fast you can R/W a global variable. I use it primarily to reduce a faster input down to a slower module like the digital output.