"The Capacitance Principal" of level measurement says the output
signal in milliamps is dependent on the formula :
Capacitance (C) = Dielectric Constant (K) * Area of Parallel
Plates (A) ÷ Distance Between Parallel Plates (D) or C = KA / D.
In a level measurement application, the dielectric constant “K” is a
value greater than 1. The value “A” is dependent on the diameter and
length the level probe. The value “D” is the distance from the probe to
the tank wall, ground reference probe or concentric tube. Consequently,
capacitance (C) and the resultant mA output increases as the dielectric
constant increases, the probe diameter and length increases, and the
distance from the probe to tank wall (ground probe or tube), decreases.
What Is Capacitance?
MLST & MLXT - 4220 capacitance level transmitters are for both sanitary and industrial level transmitter
applications. They provide a continuous 4-20mA, 20-amA, 1-5VDC or 5-1VDC analog output proportional
to the material level in any shaped tank. They can be used for conductive, non-conductive liquids and moist
MLST & MLXT - TEMP - 4220’s are combination level / temperature transmitters geared for both sanitary
and industrial applications. In addition to having all of the standard specifications, they provide 2 separate
4-20mA outputs measuring level and temperature with one probe and one tank connection. Temperature
ranges from -100˚ to 1,000˚F.
Continuous Level Transmitters . . .
• Resolution to better than 1 part in 10,000
• Accuracy and repeatability to less than 0.1% of span
• Microprocessor based transmitter with on board digital to analog conversion assuring negligible output
current error of 0.003%
• Linearity of better than 0.003% over industrial temperature range of -20˚F to 160˚F
• Designed with most up to date surface mount, integrated circuits and components
• Standard range of 0.0001 picofarads to 15,000 picofarads allowing the 4220 to span 4-20mA
over 1 inch of water, (high sensitivity) or hundreds of feet of water (low sensitivity)
• Non interacting zero and span
• Cancel Coat™ circuitry and superior resolution eliminate the readout errors cause by
conductive coatings on the sensing probe
4220 Standard Specifications . . .