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Datasheets and User Guides

App Notes

Software & Driver


3.2 - LJcounter

Reads the LabJack counter and provides the current frequency or count.

Figure 3.2-1. LJcounter

Figure 3.2-1 shows the LJcounter window:

  • Interval (seconds): Specifies the interval, in seconds, between calls to the DLL function “Counter”.
  • Measurement Type: If set to “Frequency”, this application divides the count by the interval to determine frequency in Hertz, and automatically resets the counter every read. If set to “Count”, the measurement is simply the current reading from the counter.
  • Measurement: Displays frequency or count, depending on “Measurement Type”.


I have 2 questions for measuring S0 Signals from a power meter:

1 is the signal connection to CNT equal to the connection to IO (100kOhm, 5V)

2. is the counter counting independing on running U12 reading software



1.  See the electrical specs in Appendix A of the U12 User's Guide.  It is similar to an IO line in that it is 5V logic, has 1500 ohms of series impedance, and has a 1 Meg pull-down to ground.

If you are using it with a dry contact, you should add a stronger pull-down such as 100k or even 10k, or you could use a 10k pull-up if you want to reverse the logic.  See Figure 2-5.

2.  Yes, the counter is a hardware feature so it counts on its own.

tricky solution, finally:

I have seen the voltage signal as wanted, when using  LJStream only. So I connected one wire of the S0-ports of the electricity meter to 5V and one to AI1. The AI1 was then connected then to CNT and it counts now! But I don't know why is does not work when directly connected to CNT- even if I use pulldown resistors. May be the signal is to noisy. I have seen quite some noise  from 0.6V- to 2.4V when using LJStream. 


Something definitely does not sound right.  If you have any detail about the meter with this S0 output, please start a forum topic and we can look into it there.