The easiest way to do this is to measure the empty space at the top of the tank using a measuring tape marked in inches. (See Figure 7).
Note: When making your measurement it is difficult to measure directly from the inside top surface of the tank to the asphalt surface. It is much easier to measure from the bottom edge of the manway to the surface of the asphalt. If you do that you will need to make a separate measurement to determine the distance from the edge of the manway to the topmost surface inside the tank. Then you should add the two measurements together as indicated in Figure 7.
Make this measurement while the tank is well over half full. Subtract your empty space measurement from the inside height of the tank shown in Figure 8.
Your final answer should match the number of inches displayed on the transmitter and controller, within one inch.
If the indicated level differs much more than an inch try and find the cause.
Start by checking the full scale blind setting of the transmitter. Make sure it is properly set for the asphalt actually stored in the tank based on the specific gravity of the asphalt at its storage temperature. Use the information under the heading “resetting the transmitter” to determine the correct settings.
Be aware that debris or anything blocking the port where the transmitter connects to the tank will cause erroneous operation of the transmitter.
LAST RESORT
In the event that measured levels differ significantly from levels indicated by the transmitter it may be possible to use a trial and error method to bring the two into agreement. You might want to try this method especially when you are not sure about the specific gravity of the asphalt stored in the tank.
But before proceeding with the trial and error method, carefully recheck your taped measurements and your arithmetic for errors. And then check the full scale blind scale setting on the transmitter to make sure it is correct.
If the two levels still do not agree, proceed with the trial and error method. It involves nothing more than changing the values of the full scale blind setting on the transmitter. Just arbitrarily increase or decrease the values until the displayed level indications agree with the level found with the measuring tape.
Each time you enter a new value and store it, check the transmitter to see how close it agrees with the level found using the measuring tape. Keep doing this until you get an acceptable match.
After using this method to attain agreement between the transmitter and measuring tape we recommend that you recheck one against the other several times over a period of a several days.
