FW actual image

FilterWatch has 2 modes of operation selectable using the ‘M’ button. The icon located on the LCD will change depending on the mode selected.

FilterWatch Mode

This is the default mode from any hard reset of the device (power switch). On a reset the user will see the display change from ‘YES’ to ‘CAL’ to ‘0,00 %’ and then disappear after a total of about 10 seconds. The user should also hear a single beep and a single flash of the green LED.

Note: Some units will display “F1.X” instead of ‘YES’ where X is the firmware revision number. ‘CAL’ is not displayed on these units.

3-days after the initial power-up, FW will start looking for a TARGET airspeed. In order for FW to find a TARGET, the airspeed must be greater than 2 mph AND we must find the SAME maximum speed 5 times within a 24 hour period.

Whether it finds a TARGET or not, FW will hibernate for 10 days. On the 11th day, FW will look for a TARGET or a COMPARE airspeed. Similar to searching for the TARGET described above, this is done for as long as 24 hours. When a COMPARE speed is found, it is check against the TARGET to see if it is lower by 25% or more. If not, will hibernate for 10 days and check on the 11th..and so on until we have determined that air flow has been restricted by 25% or more.

At anytime a user can remove FW from its base and check 2 parameters. Any button push will wake the unit up and the display will display the current clogged %. Pushing the ‘C’ button will display the number a days in the current cycle.

Anytime the device hibernates, it will wake up in FW mode. This was done in case a button is accidentally push while installing FW on its base.


FW does not sound an immediate alarm. It waits until a similar time of days from when the unit was power cycled. So if you install your device at 12 noon on Jan 1st and the your filter is clogged on March 1st, the alarm will start on March 2nd at 12 noon (or very near).  The alarm occurs every 10 seconds for 12 hours. It will repeat the following day at the same time until the the alarm is acknowledged. To acknowledge an alarm, just push any button in between beeps (while it is sleeping). AN ALARM is a flashing RED led and on OPTIONAL beep. (see next paragraph).

We also alarm on a low battery. If this occurs, the ‘LOBATT’ icon will be displayed in the lower right hand corner of the display. Its important to LOOK at the display and periodically look at  FW for a flashing RED led because if the battery is lower than 1.9volts, the beep WILL NOT SOUND. The batteries MSUT BE CHANGED at this point.

In order to keep the costs down, we use an internal clock for the 24 hours timer. If the alarm time of days starts to wonder, just reset the device with the power switch then next time you are ready to change the filter.

If you plan on using the rear connector to wire over to a relay, you will need the pinouts that we have yet to supply but the internal reed relay of FW toggles at the same point as the current beeper. Most devices do not have the relay. To see if you have a relay, the battery cover can be removed and you will see a 2-pin jumper installed on the board. The jumper must be ON to enable the relay.

Fine Details

Please review FAQs for some fine details regarding some WHAT IF scenarios.

Sensor Mode

The second mode we support on the crowd funded devices is called ‘SENS’ mode. We formerly referred to it as anemometer mode and to some extent, we find that is the best use of the mode.

Sensor mode has 6 parameters that can be displayed.

When entering sensor mode for the first time, the current airspeed in MPH will be displayed. This airspeed will take about 4 seconds to settle. The user may see the speed rise to as much as 10mph before settling to actual speed. This is due to heavy filtering that is required with our method. A user may also see a lag in the display as well. The user will also notice that the LED is flashing, each ON and OFF cycle results in a display update. If there is heavy turbulence, the updating of the display will be intermittent.

Pushing the ‘C’ button will cycle to the airspeed in KPH. OK, we admit it, we cheated here because we wanted to lean toward NO setup by the user. The user might notice that the display doesn’t change immediately, this is due to when we decide to change the display. We change the parameter at the same point that we would update the display and so turbulence affects the responsiveness of the parameter change-over.

The third parameter is ambient temperature in degrees F and the fourth is degrees C. These take a few seconds to settle as well. This is due to the fact that you just got done looking at airspeed, which heats up the PCB and in turn affects the temperature by about 2 degrees C.

The 5th parameter is battery power. Things start getting a little unstable around 2 volts. In fact, each time FW wakes up for any reason, we check to make sure the battery is above 2 volts. If NOT, we loop forever until the batteries are changed.

The 6th and final parameter is humidity. This was a bit of a goof on our part. First we selected a sensor that was discontinued after we ordered it. (We had a chance to cancel) Secondly, the sensor is mis-applied in that it is very slow. need an analog sinewave input..and so on. We used a little ‘software VooDoo’ (I think I’ll make a T-Shirt with that) to get the thing to work as expected. We got about 85% there and when they settle, they hit pretty good. So there is the 15% that will not work very well or even at all. We do not look at humidity on final test so if you get on that does not work, all we can do is apologize. If you had specifically requested humidity or selected a humidity version in the very last crowd fund. We have you covered.