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Teledyne Hastings: 200 Series RoHS, Turndown Defined, Flow Service Plans
Teledyne Hastings has completed the transition of his inventory, and we are proud to announce that THI entire line of 200 Series flow meters and flow controllers are now RoHS compliant! Most of THI products are now certified RoHS. However, there are a few of the older instruments that have not been converted yet. If you have any questions about the RoHS status of any of THI products, please contact us.
The turndown ratio of a Mass Flow Meter (MFM) or Mass Flow Controller (MFC) defines the usable range for which it can operate while maintaining its published accuracy. It can be expressed using the following formula:
A flow meter with a large turndown ratio will have a large operating range. This can also be indicative of the flow meter's cost. For example, variable area flow meters (rotameters) typically have lower turndown ratios compared to thermal mass flow meters.
Most analog mass flow meters have an accuracy of ± 1% of Full Scale (FS) and have resolution better than 1%. The usable range is from 1% to 100%. They will have a turndown ratio of 100/1 or more commonly expressed as 100:1. Digital flow meters will have an even greater turndown ratio due to their higher accuracy.
Most analog mass flow controllers also have an accuracy of ± 1% FS. However, they typically have an automatic valve shut circuit that closes the valve at flow rates below 2% of FS. This is to ensure full valve closure in the event of a small zero offset. The usable range is from 2% to 100%. Since measurement is not possible below 2%, these will have a turndown ratio of 100/2 = 50/1 or 50:1.
Teledyne Hastings created the Flow Service Plan (FSP) as a convenient way for loyal flow calibration customers to save on their metrology expenses. It is very simple: when a customer buys an FSP, they are paying for two flow calibrations on a particular flow instrument and getting the third flow calibration, on that same unit, at no charge. FSP can be purchased at any time during the life of a flow instrument, but are typically issued when the instrument is first sold.
Related products
HFM 200 Mass Flow Meter / HFC 202 Flow Controller with LFE
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Teledyne Hastings