Sensors output frequency to fast for the DCS what to do???

M

Thread Starter

Mudi

Hi All,

Thanks for all your help before and I'm also sorry for the post before. I wasn't sure of what I was doing and looking for but now I have a better understanding of what I want so I have reworded the question again so here I go again:). Like I said before I have a sensor Banner (L-GAGE LG10 Series) Laser Gauging Sensor which provides a variable output of 4 to 20 mA and the sensor is measuring the deflection of a moving object (vibration of a high pressured pipe line). The sensor can connect to DCS and everything the only problem is the sensors output frequency is to fast for the DCS. What I want is a device of some sorts that can look at the peak value from the deflection sensor and hold the value for a set amount of time so it can trend an output on the DCS for setting alarms and for monitoring purposes?
 
C

curt wuollet

First, I'm surprised that the sensor is that fast. Second, what you are looking for is probably not in the PLC or DCS field. Acquisition times for analog inputs are generally in the 1-10 mSec range or more. Third, current loops, because of their high impedance nature, are not noted for speed. And forth, if you are going to do anything with the data set, you really need time coherence to make the sampling meaningful. If the sensor is indeed fast enough for what you want to do, you would probably be better off with a PC and a DAQ card to acquire the samples. Many can acquire a set of samples with crystal clock precision and uSec sample times. You could then have the PC do the math and present the data to the DCS. There are also fairly inexpensive accelerometers available if a contact measurement is acceptable.

Regards,
cww
 
Hi

may be fast data logger is an option? check google for data logger.

hope this helps

bahawi
Regards
 
What you want is a vibration monitoring system. Forget about the Banner sensor for the moment. You are putting the cart before the horse. Type "vibration monitor" into Google and you will find lots of them. A lot of them are portable instruments (which is not what you need), but there are also lots of fixed installation types as well.

The very first thing you have to do though is figure out what the vibration frequency and amplitude are that you are interested in. The maximum frequency response for the Banner L-Gage by the way is 450 Hz. Is that fast enough for your application? Or, is the pipe too fast for your sensor?

What I would really suggest that you do is to talk to a rep for a vibration monitoring company and tell him the goal that you are trying accomplish, and let him recommend a complete package for it.

Vibration monitoring is a bit outside of my field. I do know test and instrumentation however, and I know that what you are trying to do has a lot more angles to it than you think it does.
 
W
Get a frequency divider. Most of the I/O companies make them. They are also known as pulse scalers or pulse dividers. What it does, basically is to scale the pulses to a frequency that the DCS i/o can see.

Good luck.

Walt Boyes
Editor in Chief
Control and Controlglobal.com
www.controlglobal.com
wboyes [at] putman.net
 
B
Use the voltage output option, and put a capacitor across it. That will act as a filter and smooth out your readings.
 
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