DP820 used for a flow totalizer , to read pulses.
I am using DP820 to count the pulses coming from a flow totalizer.
When i read the counter value after a certain flow , when i compared the mA based totalizer and the counter based value , have not got any correlation between the two.
Is there any special configuration to make for DP820 to give me the totalized value.
Does the counter only count the number of pulses.
I have configured the frequency input to receive the flow.
Could anyone please let me know which is more accurate , counting the pulses or is the frequency configuration ?
Which one is "better" or more accurate depends on your installation. You need to consider things like ...
- What is the typical frequency of your pulse input ? The DP820 is a high speed counter and will be more accurate if your pulses are occuring many times per second ( up to and over 100 kHz) . The pulse counts are then converted to a frequency measurement by the DP820. So counting pulses or using frequency is really just the same thing, but counting pulses makes more sense when one pulse is a fixed amount of flow.
- However, If you are only getting pulses every few seconds, then a DP820 is not very accurate and using frequency measurement becomes a very poor method of totalizing - You need to receive several pulses in a fixed period of time in order to be able to calculate a frequency. If you only get 3 pulses in 9 seconds, then it takes you about 10 seconds to calculate a measurement so its very innacurate and very slow to update. In this case, you are much better off using a normal digital input to count pulses.
- Where is your mA reading coming from ? An independant flow meter or the same flow totalizer ?
- When you say you "have not got any correlation" what does that mean. Are both your totalizers completely wrong ? Is one of them right ( compared to a manual calculation from your flow meter ) ? Are you sure you dont have an instrument installation or measurement problem rather than a DCS calculation problem ?