NOSHOK KING-GAGE 5900, Operation & Calibration Manual

Page: 10 / 12

page 10
Model 5900 D/P Module EX-1710-1
Pressure Range Calculation
There are two simple equations that can be used to
determine the actual range (span) required for the
transmitter. One of these gives the range in psid and the
other in INCHES OF WATER.
(B − A) × C
27.6807
= Range (psid)
Where . . .
A = Reserve (inches of depth from low point of tank to
sensor)
B = Full Tank (inches of depth from low point of tank to full)
C = Specific Gravity of Tank Contents
Converting LBS/GAL to Specific Gravity
If the density of the liquid is expressed as pounds per gallon
(e.g., 8.6 lbs/gal), the specific gravity can be determined
by dividing the value by 8.33 (weight of water per gallon).
Examples—Pressure Range Calculations
A typical tank gauging application is illustrated in Figure
1. The “reserve” represents the distance from the lowest
point on the bottom of the tank to the installed sensor.
“Full” is the level of contents at which the tank is filled
to capacity (or may be some point below the tank top, as
desired). The liquid contents in the tank is water @ 1.00
specific gravity.
C = 1.00 (Specific Gravity)
B = 382" (Full Tank)
A = 30" (Reserve)
(382 − 30) × 1.00
27.6807
= 12.72 psid
(382 − 30) × 1.00 = 352" water
A second tank gauging application is illustrated in Figure 2.
The “reserve” represents the distance from the lowest
point on the bottom of the tank to the installed sensor.
“Full” is the level of contents at which the tank is filled
to desired level (which is less than the actual full capacity
of the tank). The liquid contents in the tank has a specific
gravity of 1.032.
C = 1.032 (Specific Gravity)
B = 300" (Upper Level)
A = 28" (Reserve)
(300
−
28)
×
1.032
27.6807
= 10.14 psid
(300
−
28)
×
1.032 = 281" water
NOTE
—Should the calculated range exceed the upper span
limits of the transmitter, the next higher range is required.
If the calculated range falls below the lower span limits, a
lower range transmitter is required (to obtain 20 mAdc).
Figure 1
Figure 2
When Output will be Less Than 20 mA . . .
Maximum Pressure Below 3.00 PSID
When the nominal 5 psid transmitter is used on an
application whose maximum pressure is less than 3.00 psid,
the full calculated range output will be less than 20 mA.
To determine the actual milliamp output of the transmitter
when the maximum applied pressure is below the lower
span limit, use the following formula:
(16
×
Calculated PSID) + 4 = mA Output
3.0
Other Ranges
The above formula may also be used for other nominal
range transmitters if maximum applied pressure will be
less than the adjustment range allows. Merely divide by
the lower span limit PSID value (see page 4) in place of the
“3.0” shown in the formula.
A
B
Water
1.00 SP. GR.
Sensor
A
B
Milk
1.032 SP. GR.
Sensor
A
B
Water
1.00 SP. GR.
Sensor
A
B
Milk
1.032 SP. GR.
Sensor