Troubleshooting a tank monitor

This guide will help you identify and resolve most issues with your tank monitor on your own. Look in the list below to see what you’re experiencing, and go to the corresponding section. Each section explains what to check and what to do if the problem isn’t resolved.

If this guide doesn’t help, please contact us at help@calculus.group.

1. Safety first

You are working on or near a diesel tank. Therefore, always keep the following in mind:

• Never work on the tank, the sensor, or the module while the tank is being filled or refueled.

• No open flames, no smoking, and avoid sparks near the tank.

• Keep absorbent material or a drip pan on hand when working on the sensor.

• Wear gloves and safety goggles.

• Always follow the safety rules that apply at your site.

2. Quick overview

3. What is normal?

Not every deviation is a problem. The following behavior is normal:

• Measurements
  The module measures the level every hour and sends the data to the portal.

• GPS position
  The module automatically determines its position every 12 hours. A position that is a few hours old is therefore normal.

• After refueling
  Immediately after refueling, the level may deviate slightly for a few readings. This corrects itself automatically.

• After calibration
  The new volume will not appear until the next measurement.

• Summer and winter
  The sensor actually measures the weight of the diesel in the tank. The portal converts this to liters. Because diesel expands when it’s warm and contracts when it’s cold, the displayed volume may differ slightly from a dipstick reading when there are large temperature differences.

• Raw sensor value
  In the “Last known Raw Sensor Data” widget, you’ll see the value transmitted by the sensor, in milliamps (mA). A normal value ranges from 4 mA (no diesel above the sensor) to 20 mA (the sensor’s maximum measurement range).

4. Problems and solutions

4.1 The module is no longer sending data (offline)

What do you see?

No new data is coming into the portal. You can see the time of the last message in the “Edit Asset” panel, under “Current Activity”.

What can you do?

1. Check the batteries
   If a new module goes offline shortly after activation, dead or incorrect batteries are the most likely cause. Replace them as described in section 6.

2. Check the module’s location
   The module requires cellular coverage. A metal enclosure, a metal cover, or thick concrete can block the signal.

3. Restart the module
   Remove the batteries for at least 5 minutes, then reinsert them. The module will then reconnect and acquire a new GPS position.

4. Test in a different location
   If the module still does not come online, test it in a location with good cellular coverage and a clear view of the sky, away from any tank housing or metal enclosure.

No solution?

Is the module still unable to connect even in an area with good reception? Please contact us at help@calculus.group.

4.2 No GPS position or an outdated one

What do you see?

No GPS location is visible, or the location is more than 12 hours old.

What can you do?

1. Ensure an unobstructed view of the sky
   The module must not be located under a thick metal or iron cover, nor should it be shielded by the tank, metal structures, or thick concrete. Tall buildings in the vicinity can also interfere with reception.

2. Request a new position
   Remove the batteries for at least 5 minutes and then reinsert them. The module will then immediately search for a new position.

3. Or use the GPS button (latest modules only)
   Some newer Hawk modules have a button on the side of the housing. Press the button to immediately search for a GPS position. Once a GPS fix has been obtained, press the button again to disable this mode. If the button remains enabled, the module may continue attempting GPS acquisition, which can significantly increase battery consumption.

Future hardware revisions will include a spring-loaded button that automatically returns to its original position after being pressed.

Important!

Even a module that can't find a location will continue searching for a long time, which drains the battery. Therefore, make sure you have good GPS reception right from the start of installation.

No solution?

If the module still cannot determine its position even when placed in a location with an unobstructed view of the sky, please contact us at help@calculus.group.

4.3 No sensor data

What do you see?

The module is online, but no sensor data is coming in.

What can you do?

1. Check the connection
   Is the sensor connected as described in the installation manual?

2. Check the connector
   Disconnect the connector, check that the contacts are clean, dry, and undamaged, and reconnect it until it is securely fastened.

3. Check the sensor cable
   Inspect the entire length of the cable to ensure it is not kinked, crushed, cut, or damaged.

4. Wait for the next measurement
   See if data is coming in again.

5. Replace the sensor (see section 5)
   If data starts coming in after that, the old sensor was defective.

No solution?

Are you still not receiving any data even with the backup sensor? If so, the problem is likely with the module. Please contact us at help@calculus.group.

4.4 Other data is displayed, but not the fuel level

What do you see?

The module transmits data such as GPS location and battery voltage, but the fuel level does not appear.

Why does this happen?

The portal calculates the fuel level using the data (metadata) from the asset to which the module is linked. If multiple assets are linked to the same module, the portal does not know which data to use, and no level is calculated.

What can you do?

1. In the portal, open the “Gateways” page and click on the gateway you want to check. The “Edit Gateway” panel opens. Go to the “Data Sources” tab and click on the arrow behind a data source. A new panel opens listing all assets linked to that gateway.

2. Check how many assets the module is linked to.

3. Is the module linked to more than one asset? If so, unlink the assets that do not belong, so that exactly one asset remains.

4. Wait for the next measurement.

Important!

Always link exactly one module to one asset. Linking multiple assets to a single module will result in missing or incorrect data.

No solution?

If the level still doesn't appear after the next measurement, please contact us at help@calculus.group.

4.5 The displayed tank capacity is incorrect

What do you see?

The capacity or volume listed in the portal differs from that of the actual tank.

What can you do?

1. View the asset’s metadata
   Open the “Assets” page and click on the asset you want to check. The “Edit Asset” panel opens. Go to the “Metadata” tab and verify that the following variables have the correct values:

   1. Diameter_Cylindrical_Tank
      The diameter of the cylindrical tank in cm.

   2. Length_Cylindrical_Tank
      The length of the cylindrical tank in cm.

   3. Tank100pct
      The mA value when the fuel tank is full.

   4. TankLiter
      Amount of liters in the fuel tank when full.

   5. AdBlueTank100pct
      The mA value when the AdBlue tank is full.

   6. AdBlueTankLiter
      Amount of liters in the AdBlue tank when full.

2. Is the data incorrect?
   Adjust it and recalibrate the sensor (see section 7).

3. How high is the sensor located?
   If the sensor is not positioned at the very bottom of the tank, it will not measure the diesel below the sensor. In that case, the lowest volume displayed will never be zero.

No solution?

Is the capacity still incorrect even after recalibration? Please contact us at help@calculus.group.

4.6 Significantly fluctuating values

What do you see?

The level or raw sensor reading fluctuates up and down even though the tank is not being refueled or filled.

What can you do?

1. Check the sensor cable
   The sensor requires a small vent to measure correctly. This vent runs through the connector. A kink, sharp bend, or any spot where the cable is pinched will interfere with the measurement.

2. Make sure the connector is dry
   Moisture or water in the connector or the vent can interfere with the measurement.

3. Check the tank’s vent
   Make sure the vent opening isn’t clogged by dirt, insects, or a cap.

4. Take pumping and refueling into account
   Minor fluctuations during or immediately after pumping or refueling are normal.

5. Replace the sensor
   See section 5 if the fluctuations persist.

No solution?

Do the readings continue to fluctuate even with the reserve sensor? Please contact us at help@calculus.group.

4.7 Raw sensor value below 4 mA or above 20 mA

What do you see?

The “Last Known Raw Sensor Data” widget displays a value outside the normal range of 4 to 20 mA.

What can you do?

• 0 mA or nearly 0 mA
  The sensor is not establishing a connection. Check the connector and the cable as described in section 4.3.

• Between 0 and +/-4 mA
  The sensor may be connected incorrectly, or there may be negative pressure in the tank because the tank vent is clogged. Check the connection and the tank vent.

• Above 20 mA
  The sensor is measuring beyond its range. Check that the tank vent is clear to prevent excess pressure from building up in the tank, and ensure the tank is not overfilled.

If the reading remains abnormal, replace the sensor with the spare sensor (see section 5).

No solution?

Does the value remain outside the 4 to 20 mA range even with the reserve sensor? Please contact us at help@calculus.group.

4.8 The level is off immediately after filling

That's normal. During filling, temporary pressure may build up in the tank, causing the sensor to read slightly too high or too low immediately after filling. The reading will correct itself automatically with subsequent measurements.

Hint!

If the level is still not normal after a few measurements, check the sensor cable and the tank vent as described in section 4.6.

4.9 The volume was not updated after calibration

That's normal. The new volume won't appear on the dashboard until the next reading comes in.

4.10 Message indicating that the tank needs to be recalibrated

Diesel expands when it's hot and contracts when it's cold. For example, if the tank was calibrated in the summer and refilled in the winter, the displayed volume may differ, and you may receive a message stating that the tank needs to be recalibrated.

In that case, recalibrate the tank as described in Section 7.

5. Replace the sensor with a spare sensor

A spare sensor allows you to quickly determine whether the problem lies with the sensor or the module. The spare sensor works immediately after connection: you don't need to configure or recalibrate anything, as long as it is installed in the same location as the old sensor.

Important!

Never replace the sensor while filling or refueling.

1. Take a photo of the current installation and the connection so you can install the new sensor in the same way.

2. Disconnect the sensor’s connector from the module.

3. Remove the old sensor.

4. Install the replacement sensor in exactly the same location and at the same height as the old sensor. A different height will result in a different volume.

5. Lay the cable without kinks or sharp bends.

6. Connect the connector to the module until it clicks into place or is securely fastened.

7. Wait for the next measurement and verify that the raw sensor value is between 4 and 20 mA and that the level is correct.

8. Contact your account manager to report the defective sensor and order a new replacement sensor.

6. Replacing the batteries

New modules come with new batteries. How long they last depends on factors such as:

• the age of the batteries (their voltage decreases over time);

• extreme heat or cold;

• how often the module transmits data;

• the strength of the cellular network and GPS reception.

What kind of batteries?

Use only bobbin-type lithium thionyl chloride (LTC) batteries. Only these batteries provide the stable current the Hawk needs for the pressure sensor.

• Quantity and size: 4 x C

• Recommended type or part number: TADIRAN SL-2770/S C - 3.6V - 8.5Ah

Important!

Do not use regular alkaline batteries, rechargeable batteries, or spiral-shaped LTC batteries. Using these types of batteries will cause the module to malfunction or drain the batteries quickly.

How to Replace the Batteries

1. Carefully open the case.

2. Remove the old batteries.

3. Insert the new batteries. Make sure to observe the correct polarity (+ and −).

4. Check the silicone seal on the housing for wear or damage. A damaged seal will allow water to enter.

5. Close the housing securely.

6. After the next measurement, check to see if data is being transmitted to the portal again.

7. Recalibrating the sensor

Recalibrate the sensor if:

• the displayed capacity or volume does not match the actual value;

• you have modified the asset’s metadata;

• you receive a notification that the tank needs to be recalibrated, for example, after a significant temperature difference between summer and winter.

How to calibrate

Read the following article for detailed instructions on how to calibrate a tank monitor: Calibrating the tank monitor.

Hint!

Calibrate at a known level, for example, after filling the tank completely. Wait for a few readings after filling to ensure the measurement is stable.

8. What not to do

• Shortening, lengthening, or cutting the sensor cable. This will damage the sensor’s vent.

• Opening the sensor itself.

• Moving the sensor to a different height without recalibrating it afterward.

• Cleaning the module or connector with a high-pressure washer.

• Connecting multiple assets to a single module.

• Using batteries other than the specified LTC bobbin-type batteries.

9. Contact your support team

If the problem isn't resolved after following the steps in this guide, please contact us at help@calculus.group.
Please include the following information so we can help you more quickly:

• the module's serial number or IMEI number;

• the asset's name in the portal;

• when the problem started occurring;

• the date of the last refill;

• which steps from this guide you’ve already followed, and whether you’ve tried the backup sensor;

• photos of the module, the sensor, the cable, and the connector.