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How To Avoid Spikes In Sensor Readings Caused By EMI

If you observe sensor spikes or exceptionally high/low ranges of values, the culprit is usually electro-magnetic interference (EMI).

What generates EMI?

  • Florescent lights
  • Large motorized machinery
  • High powered cables
  • Any other device that produces an Electro-Magnetic Field

In general, increasing the distance of a sensor from the Room Alert Monitor also increases the chances of EMI causing sensor spikes. Typically, it’s the sensor cable that’s affected by EMI, rather than the probe itself.

To ensure that EMI is the cause of the issue, AVTECH recommends a series of basic tests.

Test for EMI issues

To test if EMI is causing the behavior you’re observing:

– Remove the sensor and cord from their current location.
– Disconnect any extension cords from the sensor.
– Connect the sensor directly to the Room Alert Monitor.
– Coil up the cord.
– Place the cord and probe right next to the Room Alert Monitor.

With the sensor in this coiled-up state, EMI should be minimized, and spikes in temperature or humidity are typically pacified.

If this is the case, then the cause of the spikes are, in fact, EMI.

Recommendations for environments with EMI

Unfortunately, not much can be done to prevent EMI; it can only be avoided in the monitoring environment. AVTECH suggests routing all sensor cables away from any major sources of EMI, or moving the Room Alert Monitor closer to the sensors.

If the relocation and coiled-up sensor cable tests still yield spikes, our next recommendation is to relocate the Room Alert Monitor and sensors. Move them to an isolated location, such as an office, to provide a trial atmosphere that is free of EMI.

For information on discovering your unit after it has been relocated, please see How To Discover A Room Alert Monitor.

If the sensors still experience spikes after being physically relocated, attempt to isolate the issue to a specific piece of hardware. Move the sensors to different ports and check if the spikes follow. This will tell us if the issue is related to the environment, the Room Alert Monitor, or the sensor.

Delay notifications to avoid false alerts

There is a quick workaround that generally prevents false alerts caused by EMI. When EMI strikes, it usually occurs in short bursts—often less than a second of duration. You may set a short delay in order to avoid receiving alert notifications for EMI spikes.

Delay alerts at RoomAlert.comDelay alerts in Room Alert Manager

To set the delay in RoomAlert.com:

Please follow the instructions in this Frequently Asked Question: How To Delay Actions In Your RoomAlert.com Account.

We recommend setting a delay of 5 minutes, the shortest option available at RoomAlert.com. You’ll need to delay each action associated with your alert.

To set the delay through Room Alert Manager:

  1. Open Room Alert Manager. For instructions, please see our FAQ, How to Open Room Alert Manager’s Web Interface.
  2. In the navigation bar to the left, select Alerts.
  3. Locate the alert that you wish to delay. From that alert’s menu, select Edit.
  4. In the Then… section of the alert form, change the DO THIS selection from immediately to after X seconds.
  5. Enter a number of second that is higher than Room Alert Manager’s Data Polling Interval.
    By doing this, Room Alert Manager will wait to trigger the alarm until it reaches that number of seconds.
  6. Select Save Changes to save your action delay.

For example, if the refresh rate for Room Alert Manager is 15 seconds, you can set the action to start after to 40 seconds. Room Alert Manager will be checking 3 times—once at 0, 15, and 30 seconds—for a sensor value that is above the alert threshold. In this time, any spikes will come and go, and Room Alert Manager will not trigger an alert because the quick spike did not sustain the elevated threshold for longer than 40 seconds.

AVTECH also offers Digital Shielded Temperature & Humidity Sensors for use in environments with high electrical noise or EMI. Please contact your organization’s Product Specialist if you have any questions about purchasing a sensor.
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Room Alert is Made in the USA, ships worldwide from our locations in the US and EU, and has been protecting facilities since 1988.

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Room Alert Link- Supported Firmware Updates



Current S modelsCurrent E models
Room Alert 32SRoom Alert 32E
Room Alert 12SRoom Alert 12E
Room Alert 4E
Room Alert 3E

Room Alert Manager - Compatible Devices

The latest version of Room Alert Manager supports only the devices below.

It does not support any legacy Room Alert or TemPageR models.

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Room Alert 32SRoom Alert 32E
Room Alert 12SRoom Alert 12E
Room Alert 3SRoom Alert 4E
Room Alert 3E
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