CTR-500 module reading too many pulses?

Hi. I am using a CTR-500 module as a totalizer to count the pulses coming from a turbine flow meter. The flow meter is calibrated for 1 pulse/L and our pump is displacing 5-10 L/min. The pulse's high state is about 18VDC.
The problem we are having is that when the pulse occurs, the pulse count goes up by 5-40 counts (sometimes more). The LED on the module behaves properly and matches the pulse output from the flow meter but the reading we get in NI-MAX is not right. I'm sure this is something simple that I am missing but I can't seem to get it to work right.
I have the feeling that the module is reading many false highs as the pulse is high for a good second or so. How to I get the module to count only the rising edge of the pulse and ignore the rest?
Any help is appreciated.
Thanks,
Dave

Hi Dave,
CTR-500 does use edge counting. You can perform a software check to see if it is still at a high and if it is then not do a count and if it is not the increase the count. The green ready light just indicated that the module is working in normal mode and the green status indicator light turns on when the channel is used. Have you tried using a different flow meter with this?
Warm regards,
Karunya R
National Instruments
Applications Engineer

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I have used the CTR-500 module for mesurement of motor RPM. But it doesn't have direct option to measure RPM ,
so i have count pulses for 1sec (then reset the counter) and by calculation show the result for 1min. But it varies every time ,cant give me fix RPM.
I want reliable solution for this.

min
You have not said how much the RPM actually varies from reading to reading and what the range of measured RPM is for the process. This variation can be caused by a couple of things. One would be actual variations in RPM due to changes in motor loading. What is this motor driving? Most RPM readouts use some form of sample averaging to smooth out the readings.
A second cause could be your vi. Suggest you post a copy of your vi.
In case you have not seen it, here is a link to a KB about measuring frequency with cFP. It also links to several other docs on the same subject . http://digital.ni.com/public.nsf/allkb/D8DB42F9FDC3607E862568640047F144?OpenDocument

Problem resetting count on read with fp ctr-500 counter

Using the ctr-500 module with a FP-1000. I want to reset the count of a channel on each read. The CTR-500 manual says to selecting "Reset on Read" from the Value menu. I've done that but the counter never resets when I read it. I then tried clicking on "Creat item" under channel attributes in MAX. It creates an item called "Read Reset Mode @Count Input 0" under Data Neighborhood. Added that item to the program and wrote to it with both a 1 and 0, but when I read channel 0 it still will not reset. Obviously, I'm missing something. I would appreciate any help or a simple example so I can get this resolved. Thanks, Mike
Message Edited by mike72903 on 01-31-2008 10:51 AM
Attachments:
reset count1.vi ‏15 KB

Found an example. Thanks anyway

Frequency in cFP CTR 500

Hi, I got a VI to read frequency from cFP 2020 with the CTR-500 module (Frequency Measurement.vi) in NI Example Finder. When I run this VI in LabVIEW for Windows, it's all right. But I want to run it embedded selecting the target and, when I do it, I cannot read the frequency. Does anybody knows what could be happening? Thanks

Hi letreca,
I took a look at your code and it doesn't look like
anything is really wrong there. There was one thing that I think might
help you. Because you do not have any sort of data dependencies, you
could be causing a condition where you are resetting the counter before you
read it. The best way to change this would be to connect the error out of
the Read.vi with the error in of the Write.vi.
You mentioned in your first post that you were using
Frequency Measurement.vi from the example finder (Browse > Hardware Input
and Output > FieldPoint > Advanced); however, the code for frequencia.vi
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I think you may be having an issue mentioned in the first
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Voltage loss on incoming signal to CTR-500

I have an optical sensor with at 12Vdc power supply hooked up to a CTR-500 module with the cFP-2020. I am trying to set it up to pick up the RPM of a motor. The speed range of the sensor is 1-250000RPM which is more than enough since the max I will see is 4000RPM. With the Power supply either routed through the Module or not through the module, I can see a 10V pulse on a scope comming from the sensor(when sensor line is not connected to module) But once the signal is connected to the channel I want to read it with, the signal Pulse Voltage drops to about 8.5Vdc, which is under the requirement to generate a count.
Can anyone tell me why I am getting a voltage drop? How can i fix it.

rameymm,
The 10 V you read from the sensor with a scope, what is the ground referenced to? When you are measuring the voltage at the inputs of the module, COM is tied to the ground of the 12 V power supply. It is possible that you have a common mode voltage.
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Why does Lookout receive wrong count from FP-CTR-500

Counter module flashes light count = to field pulse input device. Lookout fieldpoint object follows device count, but occassionally double counts giving wrong results. Is this a hardware problem with the counter module? A second counter in the system works as expected. Both are wired the same way and read the same way in the software and are receiving signals from like field devices.

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To rule out the possibility of this being a hardware problem in the FP-CTR-500 module, you can swap both of your FP-CTR-500 modules. I suspect that the problem will remain on the same signal/channel indicating that it is most likely a signal problem.
You may be receiving a double count as a result of noise or signal differences in the sensors wired to the various channels. To reduce the likelihood of a spurious signal causing a double count, you can enable the low pass filter on the FP-CTR-500 to reject signals above 200 Hz. If you look at the signal on a scope, you may see that it is fairly noisy and could use some filtering. Also, consider if one sensor has a longer cable run then the other or if it routes near something that may be electricall
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CTR-500 field-device power

Hello forum,
I have recently started my FP adventure, and am pretty impressed with what I have achieved so far ... Still, since I completely lack knowledge of electronics, I hesitate for the following. I have an FP-CTR-500 that is neatly counting pulses from anemometers, water-consumption counters etc. All these devices are powered through the 24VDC power that I piggy-backed from the FP1600. Now, the new counter I'd like to install takes 3VDC in the pulse-generating loop, and I wonder whether I can have this connected to the same CTR, and in what way. Can I use a separate external power supply ?! Any suggestions ?! Thanks a lot for your help,
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According to the
device specifications the CTR500 input range is 10 to 30 VDC, so your
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NI France
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Cfp-ctr-500

Hi, I have recently upgraded a system from fieldpoint modules to compact fieldpoint.
I have a cfp-ctr-500 module which I use to generate a pulse output, a terminal count attribute is used to program the length of the pulse (5-1000ms) and the output is on channel 0.
With the old system this worked very well but with the compact fieldpoint module I cannot get any output.
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Hi,
The original modules were FP-CTR-500 RS485 coms and the new modules are cFP-CTR-500 ethernet coms.
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Pulse Counting Problem CTR-500

I am using a couple CTR-500 on a compact fieldpoint setup to measure pulses from 2 energy (BTU) meters, 3 diaphragm gas meters, 2 liquid flow meters and 2 Watt-hour electrical meters. I seem to have a problem with my pulse counts accelerating upon start up of the program (up to 1000 pulses/15 minutes <- which is unrealistic for the hardware installed and then falling to 5-10 pulses/15minutes <-reasonable value). The pulse count does not correlate with the manual meter readings I have taken either, with the exception of the Watthour meters. I am unsure if it is my program, wiring, or peripheral equipment at this point.
Has anyone seen a problem like this before? I have included a couple graphs showing the raw pulse count (saved every 15 minutes) and the change in pulse count every 15 minutes.
Solved!
Go to Solution.
Attachments:
Pulse Counting Run Away.pdf ‏128 KB

Here is an example vi of how I am reading the pulses and some data processing I am doing with the signal. I have built in a totalised pulse counter to compensate for the maximum of 65535 pulses that can be counted by the module - so I do not miss pulse counts on reset.
Attachments:
Example code for counting.pdf ‏60 KB

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lication with OPC server. Can we assure that the time of reading of values for all the channels is the same?. We need to compare those 4 external counting values between them, using the 32 Khz internal clock like a time base reference. Can anybody help us?Eduardo,
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How can we substitute the invalid option "reset after read" in FP-CTR-500 + FP-1600 frequency measurement application?

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For frequency measurement information on the FP-CTR-500/502 modules. Please see KnowledgeBase Article #1TB63SUS
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/d8db42f9fdc3607e862568640047f144?OpenDocument
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CTR-500 module reading too many pulses?

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