AB High Speed Counter Card Problems

Hi

We are using an Allen Bradley High Speed Counter Card (HSCE2-1746) to count pulses from an Endress + Hauser Promass 40 Coriolis Flowmeter. We can simulate flow at slow speeds (say 1 pulse / sec) by connecting intelligently to the flowmeter, and we observe the correct counts appearing on the card input. However, we sometimes get erratic multiple counts per pulse, ie the card would read as follows:
1,2,3,5,6,8,9,10,15,16,17 etc.

The HSCC is connected to the open collector receiver on the flowmeter, which transmits for 50ms every pulse. We have used alternative flowmeters and alternative (screened) cable routes, so we don't believe we have a problem with either the flowmeter or noise.

Has anyone experienced similar multiple counts per pulse, and/or could anyone offer some advice as to how we solve this?!

Thanks, LL

Are you verifying the counts independently with an osciliscope? Could you perhaps be going forward and back sometimes when simulating slow speeds? I only did one job w/ the HSCE2 but once it was set up it was rock solid.

noise

Hi
I did only one Job using this module ,As ndzied1 said i face many problems during start up but once it's workred you have no errors.
When i use this module i face an extremely noise problems with the pulse counting even i was using a quadrature pulse encoder(mode 1),i guess that you are using this module in mode 3.
this problem have been solved when i increase the signal /noise ratio by increasing the supply voltage to my encoder to 24V instead of 5 Volt and modify the approparate jumper in the module.
Hope this help
THX

Thanks Both!

We solved the problem yesterday, as follows:

The HSCE2 installation instructions recommend the use of a 2.2k pull-up resistor, which was how we originally installed the system. The counter-card and the flowmeter transister were installed in parallel with each other, with the pull-up resistor in series up to the +24Vdc rail. The internal impedence of the HSCE2 is about 1.5k, so we were observing a "high" voltage of only 10-11Vdc when the transistor was resistive (and 0V when conductive).

We changed the pull-up resistor to 1.0k, lifting the "high" voltage to 14.5Vdc, and the card didn't miss a beat.

The minimum "high" voltage threshold is documented as 10.5V, so my presumption is that voltage fluctuation around the threshold was causing multiple counts.

LL

LL