Question 1

What is the difference between absolute and relative modes?

Accepted Answer

In absolute mode, the SA shows the actual flow rate, either in velocity (ft/sec or m/sec) or in volumetric flow (gal/min or l/min). In order to accurately display the volumetric flow, the inside pipe diameter of the pipe must be entered in the programming menu. In relative mode, the display shows a % flow based on the high and low teach performed in the application. Relative mode is preferred, especially in pipes under 2”, since it is the most accurate setting. For more accurate flow measurement in pipes under 2”, consider the SM, SV, SB or SU families.

Question 2

What volumetric flow rate can be measured in absolute mode?

Accepted Answer

Refer to the table below. In pipe sizes below 2", consider the SM, SV, SB or SU families for best accuracy. In relative mode, measurable flow rates are approximately doubled.

Line size (in)	Flow rate of liquid (gpm)	Flow rate of gas (cfm)
2	96.5	430
3	216	965
4	386	1720
6	865	3860
8	1540	6850
10	2400	10700
12	3460	15500
14	4720	21000
16	6150	27400

Question 3

What media curves are available for the SA?

Accepted Answer

Media curves are integrated for oil, water glycol (all when MODE is set to LIQU) and air (when MODE is set to GAS). Expected response times for each medium are:
Water = 0.5 sec
Glycol = 0.8 sec
Oil = 1.8 sec
Air = 7 sec

Question 4

Why do you only specify accuracy for water in relative mode?

Accepted Answer

The SA measures flow velocity at one single point. Many factors can influence the accuracy of a thermal flow sensor, including turbulence, insertion depth, medium variation, etc. Therefore, we only specify the accuracy in relative mode, where the installation conditions and flow rate are taught. We estimate the accuracy in absolute mode to be about 10 – 15%.

Question 5

How does changing glycol concentration affect the SA?

Accepted Answer

The glycol medium setting on the SA sensor is designed for a 35% glycol/water solution. Increasing the glycol concentration decreases the evaluation signal of the SA. Likewise, decreasing the concentration increases the measuring signal. For a concentration of 50% glycol, we estimate a decrease in measured value of about -25%. For a concentration of 15% glycol, we estimate an increase in the measured value of about +25%.

Question 6

Is the SA affected by media temperature changes?

Accepted Answer

It can compensate for slow temperature changes, assuming the reference element is fully inserted in the flow, but it will be influenced for a minute or two by rapid temperature changes. As the medium temperature goes from hot to cold, the SA will drift to “UL” on the display. As the medium temperature drifts from cold to hot, the SA will drift to “OL” on the display. Assuming the reference is fully inserted in the flow to measure the medium temperature properly, the SA will return to proper reading of flow after a few seconds.

Question 7

Why are there 3 IODD files for the SA sensor? Can I use moneo | configure for programming?

Accepted Answer

Because there are differences in the signal range between liquids and gases in absolute mode and all media in relative mode, each mode requires a specific IODD file. Once the operating mode has been selected using the pushbuttons on the sensor, moneo | configure can be used for further programming.

Question 8

Is a frequency output the same thing as a pulse output for totalizing?

Accepted Answer

No. For totalizing applications, a pulse output is required. A 24 VDC signal is sent every time a specified volume (e.g., 0.1 gallons, 1 ml, etc.) flows through the meter regardless of the flow rate. A frequency output provides a digital signal directly relatable to the flow rate. This digital signal can be further evaluated with counters, PLCs, etc. Frequency outputs are often used for mechanical flow meters like turbine meters. The rotational motion of the turbine, which turns according to the flow rate, is detected and converted into frequency signal.

For meters with totalizing function, please refer to the SM and SU families.

FAQs for the SA flow sensors