Load sensor is a measure of the quality signals into electrical output of the device.
1, the load cell testing principle
Load cell testing process shown in Figure 1. Weighing sensor voltage output range of 0 ~ 30mV. Testing standards are: A: unstressed zero voltage U0 ≤ 5mV; B: 20min before and after the change in output voltage range and force during maximum voltage and minimum voltage does not exceed 0.006mV, namely Uoe-U0 ≤ 0.006mV, Umax-Umin ≤ 0.006mV; C: force the output voltage during each interval of 5min variation does not exceed 0.003mV. Throughout the testing process all output voltages meet the above test criteria, then the sensor accuracy to meet the requirements, good performance; Otherwise, the sensor can not accurately reflect suffered pressure linearity error, sensor failure.
Figure 1
2, the load sensor data analysis
In traditional testing, usually using high-precision multimeter to measure the output voltage of the sensor, the staff read the data table records its biggest drawback is that you can only read one sensor data, and each switch tester, the multimeter needs 3s settling time to reading, writing data needs 1s time cause results to have a great time error, thereby affecting the determination of qualified products, such as when reading U5, the machine reads the 1st is the 1st sensor 5min the precise value of the machine 32, when read, has been to the actual time (3s +1 s) × 32 road +5 min = 422s, that is 32, the sensor on the machine, the voltage U5 is not 5min , but the 422s voltage from Channel 1 to 32, resulting in 122s time error. weighing sensor automatically detects the use of multi-channel data acquisition card, the output voltage of each channel the average read time is reduced to a few seconds to solve the traditional problem of the time error detection.
Weighing sensor sensitivity S = 1mv / v when: excitation voltage V = 12V, maximum capacity Emax = 150kg, weighing maximum capacity Max = 150kg, maximum net output signal is: weighing sensor sensitivity S = 1mv / v when: excitation voltage V = 12V, maximum capacity Emax = 150kg, weighing maximum capacity Max = 150kg, maximum net output signal is:
Excitation voltage × sensitivity × EMmaxax = 12v × 1v / v × 115500kkgg = 12mv weighing sensor sensitivity S = 2mv / v Time: excitation voltage V = 12V, maximum capacity Emax = 300kg, weighing maximum capacity Max = 150kg, maximum net output signal as follows: excitation voltage × sensitivity × MEmaxax = 12v × 2mv / v × 310500kkgg = 12mv if only the sensitivity S = 1mv / v minimum load cell static load Emin = 6kg, when the level of accuracy is C3 level, ie, nLC = 3000, there Verification scale V = Emaxn-LCEmin = 1503k0g0-0 6kg = 0. 048kg while the test described above scales scale value e = 0. 05kg. Thus, the load cell verification scale and weighing scale value, the S = 1mv / V, under the premise is basically close.
3, the detection circuit
In CXF01 Spoke Load Cell Case
Detection circuit function is to change the resistance of strain gauge resistors into a voltage output. Because of the Wheatstone bridge has many advantages, such as the effect of temperature variation can be suppressed, can inhibit the lateral force interference, can be more convenient to solve the issue of compensation load cell, etc. So Wheatstone bridge to get the load cell a wide range of applications. Because full-bridge arm bridge highest sensitivity, the same parameters of each arm, a variety of easy to offset the impact of interference, so the full-bridge load cells are used such as arm bridge. In fact, weighing sensor is a pressure sensor in principle, just not the same shape, usually there are many ways sense, but I see that with more than, for example those used weighbridge, usually eddy current. In other words, he has a trigger winding eddy current, then there is a sensor induced eddy current strength. Since this is the metal packaging the entire sensor, eddy current in the interior, under pressure deformation after, swirl the changes after amplification can read the data. Then, the packaging material of this thing, usually chosen rigid material, in short, is the general metal, such as steel, but certainly not with a very soft things. Eddy current sensing means at least a pressure sensor, it will not use the soft metal. Because even steel, even under pressure deformation so few microns, then the change in the eddy current induced in the end is enough to change the number and if it is a soft metal, called the heavy stuff, it may easily go wrong.
