Question 1

1. The SD measures mass flow rate in SCFM (standard cubic feet per minute). What is the difference between SCFM and actual cubic feet per minute (ACFM)?

Accepted Answer

Compressed air is commonly rated in SCFM, the flow rate of a gas corrected to some set of standard conditions of pressure, temperature and humidity. This provides a measurement of mass flow, which does not change as pressure, temperature and humidity changes. For the SD family, standard conditions are 1013 hPa, 15 °C and 0% relative humidity. ACFM is the volume of gas that is flowing at the actual conditions of the application. ACFM can be converted to SCFM (and vice versa) assuming the ideal gas law:

Question 2

2. Is accuracy of the meter affected by particles, oil, etc.?

Accepted Answer

Yes. Because the meter relies on thermal technology, varying amounts of contaminants will affect it. The chart below reflects air quality per the ISO 8573-1 spec.

Question 3

3. Can the SD be used for any gas?

Accepted Answer

The SDxxx0 and SDxxx1 are calibrated for compressed air. Because air is ~78% nitrogen, these meters can also be used with nitrogen, but accuracy will be about ± 5%. SD610x is calibrated for nitrogen, carbon dioxide and argon specialty welding gases. If used with other gases, the display will not be accurate. The parameter “CGA” can be adjusted somewhat if the flow rate is known. Note: helium gas molecules are very small. The SD meters are not helium tight.

Question 4

4. What is a pulse output and why is it used?

Accepted Answer

The SD flowmeters have a pulse output that is used for totalizing applications. A 24 VDC signal is sent every time a specified volume (e.g., 1 scf entered as ImPS in the menu) flows through the meter regardless of the flow rate. This pulse can be further evaluated with a counter, PLC, etc.

Question 5

5. What is the ZH4217 and how do I use it or another external pushbutton to reset the totalizer?

Accepted Answer

The ZH4217 is a kit consisting of KT6301 pushbutton, E12380 cover for the pushbutton labeled "OFF", and EVC847 y-splitter.

Setup

On the SD, change OU2 to [In.D] and Din2 to [HIGH] using the step-by-step procedures below. These procedures could be used with any external pushbutton reset.
When using the ZH4217, connect the KT6301 to channel B of the EVC847 and connect the SD sensor to channel A. Then, connect power to channel C with pin 1 to +24 VDC and pin 3 to ground.

The totalizer will be reset to zero when the pushbutton is pressed.

For 3-pushbutton SDs

Press Mode / Enter button to enter menu.
Press [▼] to EF, press mode enter button.
Press [▼] to OUT2, press mode enter button.
Press [▼] to ou2, press mode enter button.
Press and hold [▲] or [▼], until the progress bar completes. Keep [▲] or [▼] pressed until [In.D] is displayed. Release and briefly press mode enter. (ou2 will be displayed)
Press [▼] until DIn2 is displayed. Briefly press mode enter.
Press and hold [▲] or [▼], until the progress bar completes. keep [▲] or [▼] pressed until [HIGH] is displayed. Release and briefly press mode enter.

Question 6

6. Are there pressure drop charts for the SD?

Accepted Answer

No. The SD includes a straight pipe section with no internal tapering. The only restriction comes from the small measuring elements inside the flow tube, resulting in a negligible pressure drop.

Air flow meters | FAQs

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