The other day, my good friend at our German distributor contacted me with a need for some help on a Digital Flow Meter. His customer made a test rig to put the Digital Flow Meter in-line with their machines on a per-machine basis to check for flow rates and leaks. That’s a great way to use the Flow Meters. But this customer was making some bench tests and were not getting what they felt to be proper flow rate readings and their readings were not consistent between the Digital Flow Meter readout and the data pulled from the USB Data Logger.
Luckily, my colleague and his customer thought to send me some photos of their set-up as well as a data chart output from the Data Logger. These made the job of sleuthing out the problem that much easier. You see, the customer took the time to read the instructions to know about how long to make the test pipe and where to locate the meter along the length of that test pipe. So, they wanted to show me that they had 30 diameters of pipe up stream and 5 diameters of pipe down-stream per the instructions.
When I viewed their photo as you will see below, I saw everything seemed to be laid out well and assembled with good technique. But one thing stood out to me. If the 30 diameters of pipe were up-stream of the meter. That meant the airflow was coming to the meter from the right in the photo. And as you can see, the meter is sitting upright so they can see the numbers on the readout properly.
There is only one problem. In that arrangement, the meter display would actually need to be upside down. The root of the problem is that the meter was installed for ease of reading in this test procedure. The customer neglected to note that there is only one direction in which the meter can be installed. There is an arrow on the side of the meter box that indicates the direction of flow.
When you mount the meter counter to that arrow, the readings given by the meter become distorted due to how the meter works. One probe is heated to maintain a set temperature differential and if installed in reverse order, the meter overcompensates in its power applied which then messes up the reading output. The solution to this problem was to simply un-bolt the meter from the pipe and flip it over to have the right orientation. Unfortunately, this is what can happen when the instructions are not consulted in their entirety. But then again, who of us haven’t been guilty of that at some point!
The other problem the end customer was having was a mismatch of readings between their meter and the USB Data Logger. So I reviewed their output flow graph and noticed right away the problem. See the graph below:
When setting up the USB Data Logger through the software, they neglected to set the 4 mA base line to equal zero flow. So, whatever value was stored in the software ended up making 4 mA set to about 3 m3/minute according to the graph above. The top end of the flow meter’s capacity also has to be entered into the software as the 20 mA value so that the milliamp output truly mimics what the flow meter is seeing.
After a quick discussion with my colleague, he then turned to his customer to have the same discussion with them and all was working fine by the end of the day. The customer could get on to the original task at hand which was to discover leaks and baseline his machines for airflow.
If you ever have any difficulty with an EXAIR product, we have a full staff of Application Engineers who can assist you with these kinds of problems with the equipment. It is truly our goal to make sure that everyone’s experience with our company is top notch.