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load cells introduction：
Load cell is called the heart the electronic weighing apparatus. With the science and technology rapid development,
made by load cell, the electronic weighing apparatus have widely been applied to all the various occupations, also realized to measure materials fast and the industrial production process increasing and the microprocessor appearance, load cells becomea kind of essential installment in controlling and measuring from large pot/hopper/overhead track scales/automobile scale to vibratory feeding system which mixes all kinds of raw materials. At present, load cells nearly have been applied to all the domain of measuring heavy!
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Applies to the curb weight examination |
Applies to the machine capability examination
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Applies to the industrial automation domain |
Applies to the commercial measurement domain |
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Load cells Wiring Schematic Diagram:
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Red line: Input ( + )
white line : Output ( - )
Heavy line: Input ( - )
Green line: Output ( + )
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Note information:
The not special showing sensor wiring method, selects above wiringmethod! ! If the customer has the special demand, the our company maychange the wiring method!
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The resistance should the variant call the heavy sensor principle:
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The resistance should the variant call the heavy sensor is based onthis kind of principle: The elastomer (elastic part, sensitive Liang)has the elastic deformation under the exogenic process, causes to gluein his surface resistance strain gauge (transition element) alsoaccompanies has the distortion, after the resistance strain gaugedistortion, its resistance number will change (to increase or toreduce), again will pass through the corresponding metering circuit totransform this resistance change into the electrical signal (voltageor electric current), thus has completed the external forcetransformation for the electrical signal process.
Thus it can be seen, the resistance strain gauge, the elastomer andthe examination electric circuit are the resistance should the variantcall in the heavy sensor the essential several main parts. Underbriefly elaborates on these three aspects.
1、 resistance strain gauge
The resistance strain gauge is a resistance wire machinerydistribution in the basis which the organic material makes together,namely becomes a piece of strain gauge.
2、 elastomer
The elastomer is has the special shape the structural element.Its function has two, first is it withstands called the heavy sensorreceives the external force, has the reacting force to the externalforce, achieves relatively 静平衡; Next, it must have a highquality strain field (area), causes to glue quite ideally in this arearesistance strain gauge completes the strain □□ electrical signalthe transformation duty.
3、 examines the electric circuit
Examines the electric circuit the function is transforms theresistance strain gauge resistance change into the voltage output
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Naming System of Load cell / Force Transducer |
Series |
Type & Structure |
Code Number |
Materials |
Hermetic Mode |
Capacity |
Precision |
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CZL
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1:Bridge style
2:Spoke fype
3:S fype
4:Mouti-column style
5:Board Style
6:Parallel beam
7:Single bending beam
8:Shear beam
9:Double-ended fixuped beam
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01~99
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L:Aluminum
B:Stainless stell
H:Alloy steel
T:Titanium
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F:Welding
No MARK :
Other way tor seal
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C1: OIML 1000Divisions
C2: OIML 3000Divisions
C3: OIML 3000Divisions
C3D: 0.02%
G1: 0.1%
G2: 0.2%
G3: 0.3%
G5: 0.5%
G10: 1.0% |
Gives an example:CZL - 1 - 10 - H - F - 20t - C3 |
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Load cell Protection Class |
Clas |
Protection Degree |
Exprrimemtal Method |
ZEMIC Attaimable Protection Class |
Description |
Meanings |
IP5 |
Guards against the shallow water |
Not affelted by the water-sprinkle from any directions a short time |
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ZEMIC A tttainable Protection Class |
Comtinurlly spray water from any directions is more than 15 minutes |
IP6 |
Water- sprayed protection |
Not be affected by the strong water-spray from any directions in a short time |
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Cover sealed, inner adhesive protected load clees could achieve |
Continually spray wter from any directions is more than 15 minutes |
IP7 |
Soggy Proof |
Not be affected by inundating into the water in a stated pressure add time |
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Cover (or bellowed) welded, inner adhesive protected load cells or multi-layers adhesive load cells could achieve. Besides of oil-proof, waterproof, it also can proof the common corrosive gas and medium |
inundate into the 1 meter deep water for 30 minutes |
8 |
Diving Proof |
Can be dived into the water for a long time |
Decided individually |
Special required load cells could be customized |
Reference to Noational Standard of the Cover Protection Class System(P.R.C ) !
Equal to IEC529 Standard (International Electrician Association )! |
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Strain gauge structure:
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Ⅰ. Backing Glue
1.Phenolic Glue (code name:F) After common phenolic glue is modified, it has suitable rigiditystrong adhesion, good slice techonlogy, lower cost and simple operation. Especially, if it is adhibited to aluminumalloy elastimer which has larger positive creep, sensor will have a wide adjustment range. After sealed, it will be more stable.Application: manufacturing sensors.
2. Epoxy Glue (code name: H) Rigidity is excellent, temperature range is wide ( 40～120℃).Application: especially to steel load cell with big capacity and pressure sensor.
Ⅱ. Grids Foil
1. CuNi Stable performance, Good umiformity, excellent slice technique and welding performance.By heat treatment, its resistor temperature Coefficient will self-compesate to Aluminum (23) and Steel (11). It is excellent material for high precision loandcell.
2. NiCr AIFe (NnCrAICu) High resistivity and sensitivity. By heat treatment, the temp. Performance of semsitivity coefficient can be adjusted. It is fot to produce 0.03-0.05 level sensor without ex -ternal compensation.
Ⅲ. Elastic Modulus Self-Compensation
In elastomer, elastic modulus in creases with the raise of the ambient temp erature. On the con-trary , by adjusting heating treatment technology for NiCrALFe foil, strain gage s sensitivity coe-ffcient K decreases with the raise of temperature. But the method only compensates 80% of elasticmodulus. It is very suit able to manufacture 0.05 levllow cost sensors.
Ⅳ. Creep Self-Compensation
Because of internal molecules movement in elastomer, there is minor change on creep along with time when creep value ＞0. But for High polymer effect, strain gage s backing glue and Adhesive have minor change in value ＜0 range. Through experiment, we know that changing protion of strain gage end line and grid width may adjust strain gage s megative creep value, thus it compensates positive creep of all kind of elastomer, especially to aluminum alloy elastomer. |
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Strain gauge foundation general knowledge:
Structure of Strain Gages
There are many types of strain gages. Among them,a universal strain gage has a structure such that agrid-shaped sensing element of thin metallicresistive foil (3 to 6μm thick) is put on a base ofthin plastic film (15 to 16μm thick) and is laminatedwith a thin film.
Principle of Strain Gages
The strain gage is tightly bonded to a measuringobject so that the sensing element (metallic resistivefoil) may elongate or contract according to the strainborne by the measuring object. When bearingmechanical elongation or contraction, most metalsundergo a change in electric resistance. The straingage applies this principle to strain measurementthrough the resistance change. Generally, thesensing element of the strain gage is made of a copper-nickel alloy foil. The alloy foil has a rate ofresist-ance change proportional to strain with acertain constant.
Types of strain measuring methods
There are various types of strain measuring methods, which may roughly beclassified into mechanical, optical, and electrical methods. Since strain on asubstance may geometrically be regarded as a distance change between twopoints on the substance, all methods are but a way of measuring such a distance
change. If the elastic modulus of the object material is known, strainmeasurement enables calculation of stress. Thus, strain measurement is often performed to determine the stress initiated in the substance by an external force, rather than to know the strain quantity.
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Strain gauge shaping reference table1
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kind of Strain Gage |
Backong Material |
Resistance in OHMs |
Grid and Tab Geometry |
S.T.CODE.M.C |
Creep Compensation |
B |
Foil |
F |
Phenolices |
120
175
350
500
700
100
1500 |
AA |
Homo taxial |
Steel |
11 |
T5,T3,
T1,T8,T4,N4,
N6,N8,N0,N1,
N3,N5,N7,N9
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creep minus-- porsitive |
H |
Epoxy |
HA |
45lndented Slice |
Al |
23 |
T |
Specific use |
A |
Poiyimide |
GB |
Sewmi-bridge Slice |
B |
Reinforced Laminated Epoxy |
FG |
Full-bridge Slice |
Stainless Steel |
16 |
KA |
Wafer Slice |
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BF Contrast Table about BF Series Grade of Creep and Capccity of Aiuminium Alloy Sensor(Reference)
There is 0.01~0.015%F.S/30min difference between creep value of near grades
N9>N7>N5>N3>N1>N0>N8>N6>N4>N2>TO>T2>T4>T6>T1>T3>T5 |
Greep Grade |
Capacity(kg) |
Greep Grade |
Capacity(kg) |
N9 |
=500 |
N7 |
300~500 |
N5 |
200~300 |
N3 |
100~200 |
N1 |
50~100 |
N0 |
30~50 |
N8 |
20~30 |
N6 |
15~20 |
N4 |
10~15 |
N2 |
60~10 |
T0 |
5~6 |
T2 |
2~5 |
T4 |
1~2 |
T6 |
0.51~ |
T8 |
0.3~0.5 |
T1 |
0.2~0.3 |
T3 |
0.1~0.2 |
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