Why Capacitance

One of the questions we get asked frequently is why use capacitance?  Resistive sensors have been used for a long time…so why change?  Why now?

Need for Capacitive Load Cells?

What is Capacitance?
  • a. It is the ability of a system to store charge. So if you take a set of parallel plates and apply a potential difference to it (Voltage), then for a brief time interval, electrons move from one plate to the other (a small current is generated) until it reaches a state of equilibrium (the current stops). The charge gets stored between the two parallel plates

 

Why Capacitance

 

    • b. The amount of charge that can stored (its Capacitance) depends on the area between the plates, the distance between the plates and the dielectric constant between the plates.
    • c. The formula for the Capacitance of the system can be shown as:
    • C = Er*E0*A/d where Er is the dielectric Constant, E0 is the Permittivity of free space, A is the area of overlap between the plates and d is the gap between the plates

 

Why Capacitance graph

 

    • For Air, Er=1 and E0 is a constant equal to 0.00854 picoFarad/mm
    • So if you have two small overlapping discs of radius=5.6 mm and the gap between them equal to 0.25 mm, then the Capacitance of the system- C - is given by C = (1.0)*(0.00854)*(3.14159)*(5.6)2/(0.25) or 3.4 pF
    • If the gap between the plates changes to 0.17 mm then the capacitance increases to 4.9 pF
    • That is a change of 1.5 on 3.4 or 44.11%

 

Why Capacitance graph 2

 

How do Resistive Load Cells Operate?
Mechanical Advantage of Using Capacitive Sensing Techniques
Form Factor Advantages of Capacitive Sensors
Electronic Measurement Advantages of Capacitive Sensors
Versatility of Capacitive Sensors
Cost of Manufacturing
High Sensitivity, Small Size, and Low Cost
However, note that, despite these advantages, capacitive load cells may not always be appropriate for monitoring applications that require high accuracies over long periods of time and when used in environments with changing temperatures and moist . We recommend using the capacitive load cells for applications that require a quick measurement where the initial conditions can be zeroed out and where the environment is maintained at steady room temperature and humidity conditions. Please consult Loadstar Sensors for advice on the most appropriate sensor for your application.
iLoad Series

iLoad

iLoad

Low Profile Digital Load Cell with UART/USB Output
Capacities: 50 lb, 100 lb, 250 lb, 500 lb
Size: Dia 3 inch, 0.5 inch high
Accuracy Class: 0.25% of Full Scale
Compensated Temp Range: 20C to 30C 

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iLoad TR

iLoad TR

Tilt Resistant Digital Load Cell with UART/USB Output
Capacities: 10 lb, 50 lb, 100 lb

Size: Dia. 3 inch, 1 inch high
Accuracy Class: 0.25% of Full Scale
Compensated Temp Range: 20C to 30C 

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iLoad Pro

iLoad Pro

Digital Load Cell with UART/USB Output
Capacities: 50 lb, 100 lb, 250 lb, 500 lb, 1K lb, 2.5K lb, 5K, 10K lb
Size: Dia 3.25 inch, 0.5 inch high
Accuracy Class: 0.25% to 1% of FS
Compensated Temp Range: 20C to 30C 

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iLoad Flex

iLoad Flex

Thin Flexible Miniature Load Cell with UART/USB Output
Capacities: 10 lb

Size: Dia. 10 mm, 3 mm high
Accuracy Class: 1-2% of Full Scale
Operating Temp Range: 20C to 30C 

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iLoad Mini

iLoad Mini

The smallest, thinnest capacitive load cell we offer
Capacities: 10 lb, 50 lb, 100 lb, 200 lb
Size: Dia. 1.25 inch, 0.25 inch high
Accuracy Class: 0.5% of Full Scale
Compensated Temp Range: 20C to 30C

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iLoad Mini Stud

iLoad Mini Stud

The mini load cell for tension/universal
Capacities: 10 lb, 50 lb, 100 lb, 200 lb
Size: Dia. 1.25 inch, 0.8 inch high
Accuracy Class: +/- 0.5% tp +/- 1% of Full Scale
Compensated Temp Range: 20C to 30C

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iLoad Mini Pro

iLoad Mini Pro

Low Profile Digital Load Cell with UART/USB Output
Capacities: 50 lb, 100 lb, 250 lb, 500 lb
Size: Dia 3 inch, 0.5 inch high
Accuracy Class: 0.25% of Full Scale
Compensated Temp Range: 20C to 30C 

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iLoad Mini Pro Stud

iLoad Mini Pro Stud

Digital Load Cell with UART/USB Output
Capacities: 50 lb, 100 lb, 250 lb, 500 lb, 1K lb, 2.5K lb, 5K, 10K lb
Size: Dia 3.25 inch, 0.5 inch high
Accuracy Class: 0.25% to 1% of FS
Compensated Temp Range: 20C to 30C 

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Comparison of Capacitive Load Cells

  miniature load cell iLoad Mini Bite iLoad Mini Pro iload mini pro threads with label v 2 digital load cell iLoad TR Load Cell

digital load cell

  iLoad Mini
Load Cell
iLoad Mini
Load Cell
iLoad Mini Pro
Load Cell
iLoad Mini Pro
Load Cell
iLoad Low Profile
Digital or Analog
iLoad TR
Digital or Analog
iLoad Pro
Digital or Analog
Diameter 1.25 in. 1.25 in. 2 in. 2 in. 3 in. 3 in. 3.25 in. to 5 in.
Height 0.25 in. 0.25 in. 0.8 in. 1.925 in. 0.5 in. 1.2 in. 0.66-0.90 in.
Capacity 10, 50, 100 & 200 lb. 10, 50, 100 & 200 lb. 500, 1K, 2.5K, 5K, 10K lb. 500, 1K, 2.5K, 5K, 10K lb. 50, 100, 250 & 500 lb. 10, 50, & 100 lb. 50, 100, 250, 500, 1K,
2.5K, 5K, 10K lb.
Best Accuracy* ± 0.5% of FS ± 0.5% of FS ± 1% of FS ± 1% of FS ± 0.25% of FS ± 0.25% of FS ± 0.25% of FS
Mode of Use Compression or
Tension or
Universal
Compression Only Compression Only Compression or
Tension or
Universal
Compression Only Compression or
Tension or
Universal
Compression or
Tension or
Universal
Cable Strain Relief No
(USB Type MiniB)
No
(USB Type MiniB)
Yes
(USB Type MiniB)
Yes
(USB Type MiniB)
No
(USB Type A)
Yes
(USB Type A)
Yes
(USB Type A)
Signal Conditioner DQ-1000 or DQ-4000
or DS-4000
DQ-1000 or DQ-4000
or DS-4000
DQ-1000 or DQ-4000
or DS-4000
DQ-1000 or DQ-4000
or DS-4000
Built in to
Load Cell
Built in to
Load Cell
Built in to
Load Cell
Output Options Frequency (base),
Serial TTL or USB
(with DQ-1000)
Frequency (base),
Serial TTL or USB
(with DQ-1000)
Frequency (base),
Serial TTL or USB
(with DQ-1000)
Frequency (base),
Serial TTL or USB
(with DQ-1000)
Serial TTL or USB Serial TTL or USB Serial TTL or USB
Off Center Loading
Compensation
No
(Force applied Axially)
No
(Force applied Axially)
No
(Force applied Axially)
No
(Force applied Axially)
No
(Force applied Axially)
Yes
(Can handle small off center loads)
No
(Force applied Axially)
Compatible Display DS-3000-Pro-1 or
DS-3000-Pro-4 
DS-3000-Pro-1 or
DS-3000-Pro-4 
DS-3000-Pro-1 or
DS-3000-Pro-4 
DS-3000-Pro-1 or
DS-3000-Pro-4 
DS-3000-Pro-1 or
DS-3000-Pro-4 
DS-3000-Pro-1 or
DS-3000-Pro-4 
DS-3000-Pro-1 or
DS-3000-Pro-4 
*With TARE at room temperature
Looking for the best load cell for your application?