Frequently Asked Questions

Q1:  How do I connect the WaterFeature8 to my computer?

Q2:  How much power does the WaterFeature8 consume?

Q3:  At what ambient temperatures will the WaterFeature8 reliably operate?

Q4:  What are the display ranges of the LCD HMI?

Q5:  What are the analog output ranges of the WaterFeature8 board?

Q6:  How do I calibrate sensors?

Q7:  How do I calibrate a flow meter?

Q1:  How do I connect the WaterFeature8 to my computer?


A1:  Whether you want to program a FLO EZO, collect data using LabView, or calibrate sensors to non-standard solution values, connecting your computer is easy.  You will need:

  • An RS232 adapter with male DB9 wire end to physically make the connection.  We like FTDI solutions such as these.

  • A terminal emulator program.  We regularly use Tera Term (free download) in our shop.

  • The WaterFeature8 Technical Manual, downloadable from our website here.  Read Chapter 10!

From here the opportunities are virtually unlimited.  You can collect data using the continuous output function, set the WaterFeature8 into remote state (forever, if you want), use a handful of the pre-programmed polling functions, or use encapsulation commands to communicate directly with populated EZO circuits.

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Q2:  How much power does the WaterFeature8 consume?

A2:  The WaterFeature8 is designed to nominally operate on +24 VDC power.  The maximum power consumption at +24 VDC is about 5.75 W (0.24 A).

The WaterFeature8 will also run on less than +24 VDC, and has been succesfully powered with +12 VDC.  However, at +12 VDC the analog output signals may perform erratically, particularly at long current loop wiring runs.

Voltages above +24 VDC nominal will cause damage to the WaterFeature8 board, at may potentially damage attached sensors and EZO circuits.

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Q3:  At what ambient temperatures will the WaterFeature8 reliably operate?

A3:  In general, the limiting temperature component is the 4x40 character LCD HMI screen.

     Minimum Temperature = -20C (-4F)

     Maximum Temperature = 60C (140F)


Note that the LCD module will appear sluggish at low temperatures which may obscure the display quality.  However, this does not interfere with analog output performance.


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Q4:  What are the display ranges of the LCD HMI?

A4:  Each EZO/sensor combination has a specific range of readings they are able to observe and display.  Note that these ranges are different from the analog output ranges due to the LCD character limitations and output circuit resolution.


Also, only four characters are dedicated to displaying the sensor value.  In most cases, if the reading is under 100, then one value after the decimal can be displayed.  If the reading is under 10, then two places after the decimal may be available.

Dissolved Oxygen [DO]

0.01 resolution (e.g. 2.05 mg/L)

Oxidation Reduction Potential [ORP]

1 resolution (e.g. 256 mV)


0.01 resolution (e.g. 9.08 S.U. for values below 10.0)

to 0.1 resolution (e.g. 11.5 S.U. for values 10.0 or higher)

Temperature [RTD]

0.1 resolution (e.g. 55.2 C)

or 1 resolution (e.g. 112 C)

Flow [FLO]

0.01 resolution (e.g. 0.86 gpm)

to 1 resolution (e.g. 421 gpm)

Electroconductivity [EC]

1 resolution (e.g. 35,805 uS/cm)

Carbon Dioxide Gas [CO2]

1 resolution (e.g. 215 ppm)

Oxygen Gas [O2]

0.01 resolution (e.g. 21.05 %)


Relative Humidity [HUM]

0.01 resolution (e.g. 35.85 %)

Pressure [PRS]

0.01 resolution (e.g. 0.45 inch H2O)

to 1 resolution (e.g. 120 inch H2O)

Do not confuse resolution with accuracy.  The system is only as accurate as the sensor/EZO combination.  The resolution is simply the reported value.  Refer to Atlas Scientific's website for more information regarding sensor/EZO accuracy.

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Q5:  What are the analog output ranges of the WaterFeature8 board?

A5:  The WF8 uses a 16-bit signal circuit which allows for 65,536 current values between the boundaries of 4 mA and 20 mA.

Dissolved Oxygen [DO]

Low (4 mA) = 0 mg/L

High (20 mA) = 10 mg/L

Oxidation Reduction Potential [ORP]

Low (4 mA) = -1,020 mV

High (20 mA) = 1,020 mV


Low (4 mA) = 0

High (20 mA) = 14

Temperature [RTD]

Low (4 mA) = -4 C

High (20 mA) = 112 C

Flow [FLO]

Low (4 mA) = 0 gpm

High (20 mA) = 525.2 gpm

Electroconductivity [EC]

Low (4 mA) = 0 uS/cm

High (20 mA) = 200,000 uS/cm

Carbon Dioxide Gas [CO2]

Low (4 mA) = 0 ppm

High (20 mA) = 10,000 ppm

Oxygen Gas [O2]

Low (4 mA) = 0 %

High (20 mA) = 42 %

Relative Humidity [HUM]

Low (4 mA) = 0 %

High (20 mA) = 100 %

Pressure [PRS]

Low (4 mA) = 0 inch H2O

High (20 mA) = 1,385.39 inch H2O

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Q6:  How do I calibrate sensors?

A6:  The WaterFeature8 includes a simple calibration submenu that is accessible from the Home Screen.  Each sensor type has slightly different calibration requirements.  Follow the on-screen prompts to calibrate each individual sensor.  Detailed instructions are included in the provided instruction manual, and can also be downloaded from our Downloads page.

Calibration information is stored in each specific EZO and is retained when power is turned off.  Calibration values are NOT overwritten when the AutoConfig feature is performed.

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Q7:  How do I calibrate a flow meter?


A7:  Flow meters are not calibrated the way a typical submerged probe or sensor is calibrated.  The K-value of the meter must be manually changed in the FLO EZO to modify the volume calculated per revolution of the meter.

A meter's K-value will be set up in the FLO EZO in one of two ways:


  1. For a single K-value meter:  relating the volume per pulse to the number of pulses counted.

  2. For a multiple K-value meter:  relating the volume at different revolution speeds to the observed frequency in Hz.

The FLO EZO simply counts pulses between polling times, and "does the math" whenever the WF8 requests a flow rate reading.  Therefore, the K-value memory of the FLO EZO circuit needs to be changed to revise the measurements it reports.  This involves performing a bucket test or similar field test to confirm the flow rate, and then reprogramming the EZO so that the K-value represents this new flow rate.

The procedure steps are summarized as:

1.  Gather materials

2.  Calibrate measuring vessels

3.  Find the current EZO K-value(s)

4.  Run the flow test

5.  Calculate the actual flow

6.  Calculate the new FLO EZO K-value(s), repeat steps 4 and 5 at different flow rates to gather data for multiple K-values.

7.  Update the FLO EZO K-value(s)

8.  Return the device into service, perform future re-calibrations as needed

The following example covers each step in a little more detail.

Flow Meter Calibration Bucket Test Example:


There are several ways to calibrate a FLO EZO, but for this example we will use one common way which is called a bucket test.

Step 1:  Gather materials


Obtain an appropriately large container depending on meter size.  Maybe a 5 gallon bucket?  Maybe a 50 gallon drum?  Maybe a 275 gallon tote?  Depends on the meter size.  Bigger meters will require larger calibration volumes.  Use good judgement here ... the exact size is not critically important, but measuring the volumes accurately will improve the overall accuracy of the meter after calibration.

For this example we will use:

  1. large bucket

  2. smaller bucket of known volume

  3. marker

  4. stopwatch (or the stopwatch feature on your watch or smartphone)

  5. WaterFeature8

  6. Atlas Scientific FLO EZO circuit installed in any channel of the WaterFeature8

  7. DC Pulse type meter

Step 2:  Calibrate measuring vessels

For this example we fill the 5-gallon bucket with exactly 4-gallons of water using the 1-gallon pail.  Mark the water level with a permanent marker and dump the water out.

Step 3:  Find the current K-value(s) of the FLO EZO you are calibrating

Connect the flow meter and ensure the WaterFeature8 is powered ON and properly displaying the flow meter flow rate data.  If you do not know the K-value(s) of the FLO EZO you want to calibrate, there are two ways to do this:

  1. Connect to the WF8 and follow the instructions on interfacing with the EZO using Remote State and the encapsulation commands.

  2. Power off the WF8, remove the FLO EZO, and connect directly with it using a Terminal Emulator.


The instruction manual that arrived with your WaterFeature8 will show you how to do this.  Download the manual here.


Write down the K-value for use later.  For this example our K-value is K[0.25 gpm,5 pulses].  We need to know what the EZO thinks is the correct K-value before we can correct it using the bucket test.

Step 4:  Run the bucket test to establish baseline performance

If you removed the FLO EZO in Step 3, reinstall it on the WaterFeature8 now.  Otherwise, return the WaterFeature8 to Local State, or leave it in Remote State if you prefer to interface in this manner.

The bucket test involves filling the large bucket with water passing through the flow meter, and recording the time it takes to fill the known volume.


As the bucket is filling, review what the WaterFeature8 reports as the flow rate, and use a stopwatch to time the fill.


In this example, the WF8 displayed a steady value of 0.16 gpm during the fill, and the time to fill 4 gallons was 20 minutes.

Displayed Flow Rate = 0.16 gallons per minute (gpm)

Fill Time  = 20 minutes


Step 5:  Calculate the actual flow rate


Divide the known bucket volume by the amount of time it took for the bucket to fill to obtain the actual flow rate during the test.

In this example, 4 gal / 20 min = 0.2 gpm actual flow rate during the bucket test.

Actual Flow Rate, Calculated = 0.2 gpm

Step 6:  Calculate the new FLO EZO K-value(s)

According to the meter (and thus the default K-value in the FLO EZO) it should have taken 25 minutes to fill the bucket (4 gal / 0.16 gpm WF8 reading).  However, since it actually took less time to fill the bucket, 20 minutes in fact, we know that the actual flow is a bit higher than the meter reading, and we also know that the meter is under-reporting the actual flow.  Therefore, the volumetric parameter of the K-value needs to be increased so that a greater volume is reported for the same number of pulses.

The calculation involves adjusting the K-value by the ratio of the bucket test actual flow rate to the displayed theoretical reading.  This is called the adjustment ratio, R, and it is calculated as:

R = (actual, calculated) / (displayed)

In this example the K-value needs to be shifted by the adjustment ratio of

R = 0.2 gpm / 0.16 gpm = 1.25

Next, multiply the volume portion of the K-value by the adjustment ratio, R, to obtain the new K-value flow rate.

New K-value, K-new = R x K-old

K-new = 1.25 x 0.25 gpm = 0.3125 gpm

The corrected meter K-value is K,[0.3125 gpm,5 pulses].

For meters/EZOs with multiple K-values, repeat steps 4 and 5 to gather more K-value data points.


Step 7:  Reprogram the FLO EZO


Overwrite the existing FLO EZO K-value(s) with the corrected K-value by interfacing with the FLO EZO in one of the two methods discussed in Step 2, above.  Instructions for FLO EZO commands can be found in the Data Sheet on Atlas Scientific's website.

Refer to our Downloads page and check our our EZO programming instructions, or download the instruction manual for directions on how to connect via Remote State and interface with the FLO EZO using encapsulation.

Step 8:  Accurately measure flow

Continue using the installed flow meter and FLO EZO as desired, there are no other parameters to change or update in the EZO or WF8 firmware.

Flowmeter Calibration Tips:

Review the flow meter accuracy at least once every calendar year to confirm that the meter is properly calibrated.

If the meter measures flows over a wide range of flow rates, then multiple K-value data points will improve the overall accuracy of the device.  However, if the hydraulic system generally operates near a typical flow rate value, a single K-value will likely be accurate enough for process control.

When interfacing with the WaterFeature8 in Remote State, the FLO EZO will report both instantaneous flow rate and the totalized flow.  This totalized flow information is legitimate and can be used for other process control purposes.

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