Precision flow meters to measure any flow, any viscosity

How often must Max flow meters be calibrated?

What is dither and how does it affect the flow measurement?

What is the best orientation for mounting the flow meter?

For most situations, the meter can be mounted in any orientation. The special cases are:

1. High temperature where you should mount the meter so that the transmitter is to the side or below the meter. Transmitters with heat dissipating fins should be mounted sideways so that air can rise up between the fins. For other high temperature applications, mounting the transmitter underneath the meter will reduce the amount of heat which migrates into the transmitter housing.
2. If there is possibly entrained bubbles in the fluid or system it is best to place the meter on its side with fluid flowing up through the meter, or upside down so that bubbles do not collect in the measuring chambers.

Do I need flow straighteners?

Positive displacement meters are not affected by turbulence in the flow stream. It is permissible to install the meter near pumps, valves or plumbing changes. The displacement per revolution, of the meter will not change. No upstream or downstream straight runs are required.

What size filter do I need before the flow meter?

Our recommendation for the Piston series is 10 micron, for the Gear series it is 15 and 30 micron and for the helical rotor series the recommendation is 150 micron (100 mesh). For high viscosity fluids, you may have to loosen this specification to maintain an acceptable pressure drop in your system. Please consider the tight tolerances within the meter and possible sources of contamination. If dirt is present in your process, the recommended filtration level should be maintained.

How do I use a current sinking transmitter to create 12 or 24 V pulses instead of 5 V?

Max offers a variation of the Model 295 transmitter which has a transistor output such that when triggered by the software, the signal line is connected to Common. Please refer to the installation sheet offered on the Technical Documents page to review the use of this circuit to provide pulse voltages different than the 5 V pulse normally provide.

What is the difference between “Accuracy of reading” and “Accuracy of full scale”?

These two claims are only equal at the maximum capacity of the measuring device. If a meter’s accuracy is based on a percentage of its full reading capability, the error is a fixed value. For example; an error of 0.5% of full scale, in a 100 gal/min device is +/- 0.5 gpm. This is the uncertainty all of the time, so as you move away from the full scale capability, the 0.5 gpm error becomes a much larger percentage. At 50 gpm, you are risking a 1% error. At 10 gpm you have a potential 5% error. On the other hand, if the device has an error expressed as a percentage of the actual flow, then a 0.5% error of 10 gpm is only +/-0.05 gpm; a 10 times better result.

What is meant by turndown ratio?

The turndown ratio is a measure of the meter’s working range. By dividing the upper most flow rate by the minimum, measureable flow rate you determine a value that is usually presented as 3:1, 10:1 or maybe 100:1 (pronounced one hundred to one). The larger the ratio the wider the operating range of the device. Meters that cannot hold their accuracy are often specified to work in a 3:1 range. Higher precision devices that hold their accuracy may be specified as 200:1 or 1000:1 devices. Such a large range makes it possible to use the same meter for both 10 L/min measurements and 10 ml/min.

How to get an RMA (returned materials authorization)?

Call the number at the bottom of the page and speak with a Service representative, or fill out the on-line RMA form under the main menu tab
labeled “Support”

Do you supply annual calibration services?

Yes, we will recalibrate all of the meters we manufactured. We can provide “as received” calibrations and repair and certification, or “as left” calibrations.

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Max Machinery has built its reputation on helpful, friendly service. If you do not see the answer to your question, please contact us between 6:30 AM and 5 PM Pacific time. We’re happy to help and your question may make it onto this list to help others. Thanks.