MSP430FR6043: solution

Hello cash,

i need a detailed explanation for calibration

i need to check my airflow volume flow rate ....need detailed explanation how the air flow is pass for zero flow drift ....

Hi,

For calibration, it is just that the volume flow rate calculate by the software is different from the exactly volume flow rate. And the calibration process is to minimize the different between those two results, and let the calculated one close to the exact flow rate. 

For zero flow drift test, there is no flow coming through the pipe.  

Best regards,

Cash Hao

i have taken volume flow rate for transaxial transducer using uss software as well as noted the flow rate value from flow meter ....there is little bit small value changes only ....i need to calibrate the vaues taken from uss software ....how??for zero flow drift test,no flow mean how can i check...pls help to do calibration

Hi,

For gas meter, the USS library does not provide volume flow rate calibration function. It is because the gas meter is much complicate on the calibration process. There are more things will affect the total gas volume. Like temperature, pressure and etc. So, the customer usually develop their own calibration method based on their application requirement. 

For a basic concept about how to calibrate the volume flow rate. The purpose is to minimize the different between the calculated one and the measured one. 

In theory, the volume flow rate(VFR) is calculated by Meter Constant * dTOF / (absTOF1*absTOF2). Since the dTOF and absTOF is calculated by the USS library. So we need to change the Meter Constant value to make the calculated VFR close to the measured VFR from a reference meter.

For example, you totally VFR range is from 25LPH to 3600LPH. First, divide this range into some small ranges, like from 25LPH to 60LPH, 60LPH to 150LPH, 150LPH to 500LPH, 500LPH to 1200LPH, 1200LPH to 2800LPH and 2800LPH to 3600LPH. 

For a simple way, you use one dedicate Meter Constant value for each range. Use the first range for example 25LPH to 60LPH. You can run a 40LPH read from the reference meter in the pipe and read out the dTOF and absTOF value from the USS library. Then you calculate the Meter Constant value based on these data. Then when your dTOF result falls into this range again, you use that Meter Constant value to calculated the VFR. It should close to the reference meter readings in this way. 

About how to set these ranges, if you use that Meter Constant value calibrated at 40LPH. When there is a 60LPH running in the pipe, You use that meter constant value to calculate the VFR. Assume you get the VFR result at 65LPH, which has (65-60)/60 ~= 8.3% error and is beyond your accuracy requirement. Then it means this range is set too large, you need to set a small range like 25LPH to 40LPH and 40LPH to 60LPH. Use two separate meter constant value for each range to meet the accuracy requirement for each range. 

 For zero flow drift test. Please refer to this link chapter 3.2.2.2 Zero-Flow Drift. 

https://www.ti.com/lit/ug/tiduej6a/tiduej6a.pdf

Best regards,

Cash Hao

Hello cash,

zero flow drift test is an method for calibration process what is the purpose of zero flow drift test????pls help check for any other calibration techniques for find the volume flow rate ......