Analysis of common problems of the hottest encoder

2022-08-23
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Analysis of common problems of encoder

what is an encoder

encoder is a device that converts angular displacement or linear displacement into electrical signals. The former is called code disk and the latter is called code ruler. According to the reading mode, the encoder can be divided into contact type and non-contact type. The contact type uses brush output, and the brush contacts the conductive area or insulating area to indicate whether the code state is "1" or "0"; The non-contact receiving sensitive element is a photosensitive element or a magnetic sensitive element. When a photosensitive element is used, the light transmission area and the light tight area are used to indicate whether the status of the code is "1" or "0"

according to the working principle, encoders can be divided into incremental and absolute types. Incremental encoder converts displacement into periodic electrical signal, and then converts this electrical signal into counting pulse. The number of pulses is used to express the displacement. Each position of absolute encoder corresponds to a certain digital code, so its indication is only related to the starting and ending positions of measurement, and has nothing to do with the intermediate process of measurement

definition of measurement accuracy

as we all know, all measurements are rough estimates of the "real" value, that is, the measured value always has a certain error with the "real" value, so the size of such an error is usually referred to as the measurement accuracy, which reflects the ability of the measurement instrument system to truly restore the measured signal value

accuracy of incremental encoder

the accuracy of incremental photoelectric encoder has nothing to do with the resolution, which are two different concepts. Accuracy is a measure of the ability to determine the position of one pulse relative to another within a selected resolution range. Accuracy is usually expressed in angles, minutes, or seconds. The accuracy of the encoder is related to the processing quality of the light transmission gap of the code disc, the manufacturing accuracy of the mechanical rotation of the code disc, and also to the installation technology

resolution of incremental encoder

the resolution of the photoelectric encoder is expressed by the number of basic cycles of the output signal generated by the rotation of the encoder shaft, that is, the number of pulses per revolution (PPR). The number of light transmission slots on the code disk is equal to the resolution of the encoder. The more slots engraved on the code disk, the higher the resolution of the encoder. In industrial electrical transmission, according to different application objects, you can choose an incremental photoelectric encoder with a resolution of 500-6000ppr, which can reach tens of thousands of PPR at most. The encoder with a resolution of 2500ppr is usually used in the AC servo motor control system. In addition, the photoelectric conversion signal can be logically processed to obtain the pulse signal of 2-fold or 4-fold frequency, so as to further improve the resolution

what is the relationship between absolute encoder accuracy and resolution

the number of bits of the single turn absolute value encoder represents the number of code channels of the code disk. Because the binary code disk is used (the gray code is the same), its accuracy becomes several powers of 2, such as 12 bits, which is the 12th power of 2, which is 4096

the resolution and accuracy of the encoder are not necessarily the same, and the accuracy is determined by various factors such as reticle, mechanical concentricity of code disk, reading response speed, temperature characteristics, etc. If an encoder uses reticle sine wave subdivision to obtain high resolution, its accuracy is not improved, and subdivision only improves the resolution. What is the precision of the reticle before subdivision and what is the precision after subdivision, so the precision of some high-resolution encoders depends on how many lines are subdivided before

second, how to determine the maximum frequency of data polling through the SSI interface of hengstler brand

for the current location data transmitted through SSI, the following "best case" and "worst case" must be considered

The output of position data depends on several parameters, such as factor, conversion time, data format, etc. Therefore, the processing time will be different

with a processor system, you will "only" get an average response time. If you use the highest frequency of 500KHz to poll the SSI channel. That is (pulse time 2 s * 26 bits + minimum required pause time 40 microseconds) is the minimum time of about 100 s. After that, the system will need another s of time for data update, so in the "worst case" you may get the same result (position value) three times! Only by using a much faster DSP or ASIC can you get a shorter time (factor 10), or use the encoder with sin/cosine code channel applied to the motor control system

what is the difference between ac59 and AC61

the encoders of these two models are made of stainless steel. "61" type is equipped with a solid solid solid stainless steel shell and connected with stainless steel flange. Standard cable fittings are made of nickel plated brass. "This design allows complex encoder types, such as absolute encoders with bus covers and tape protected access to the inside of the encoder, such as DIP switches." 59 "includes a deep drawn stainless steel housing and is connected to a knurled stainless steel flange. Standard cable fittings are made of PVC. "This design is usually less expensive (providing encoder types that reduce some requirements): incremental encoder with cable connector, absolute encoder with cable connector and sealed housing (such as parallel single turn, SSI or BISS) 。

what is the difference between solid shaft encoder and hollow shaft encoder

solid shaft encoder needs to install flange and coupling. The hollow shaft encoder only needs a spring plate to prevent the rotation of the encoder and absorb vibration

what GSD files do you need to use when using acuro encoder

acuro AC58 series encoder you can use the same GSD file as ra58 series. The reason is: if the ra58 used is broken, the user will replace it with AC58. If the encoder code is different, the PLC (identified by the GSD file used) will not be able to connect to the AC58 encoder that replaces the ra58, so the PLC software must be modified. What we do is to make user applications more convenient

III. Dynapar brand

what is differential line driver output

differential output refers to the fact that each channel has a complementary channel, such as a and/a. Differential line drivers can help improve anti noise performance (see what/a and/b channels are used for?). Differential line drivers also allow you to have more drain or source current than Push-Pull Outputs. The differential line driver has a drain and works with the source circuit at the same time. (see what is drain or source input?) It can also help improve the transmission distance of signals

what is open collector output

an open collector output is an NPN transistor. NPN transistors allow leakage current to the common end. It can be considered as a switch, allowing the circuit to be connected to the common end after being loaded. This means that if you want to have output work, you need a power supply. The power supply must be connected to the output after the load, otherwise the NPN transistor only establishes a path to the common end, that is, the dry contact. Therefore, if you measure the open collector output voltage that is not connected to any power supply, you will not see the voltage change. If the open collector works normally, the voltage should be detected after passing through the output load

what is totem pole output

totem pole output is basically the same as push-pull output, but it is a commonly used term when referring to TTL devices. The main difference between it and push-pull output is the magnitude of drain or source current. The totem pole output has a smaller drain/source current than the push-pull output. The other main difference lies in the output voltage. The totem pole can only be a 5V DC signal, and the push-pull output will follow the input voltage

what is push pull output

push pull output is an output that allows you to connect drain or source circuits at the same time. (see what is drain or source input?) This type of output allows you to clearly see that rigid PVC foamed plastic products are widely used in many fields and the market demand is large. You may output more current and follow the input voltage than the totem pole. When the open collector output and the controller connected to the encoder cannot work, it is necessary to select the push-pull output

what is quadrature output

quadrature output means that there is a 90 degree phase shift between signals a and B. A is ahead of B or a before B ultrasound depends on the direction of rotation. This does not mean that the output will be 4 times the resolution of the encoder per revolution. The fact that the signal has a 90 degree phase difference enables the controller to determine the direction of rotation of the encoder. You must use orthogonal A and B signals at the same time to obtain the logical relationship of x2 or X4. (see what is the difference between orthogonality and X4 logic?)

why do I need a pull-up resistor

the pull-up resistor is used to "pull" the logic high voltage level to the working voltage. This is very useful when the output of the open collector does not reach the voltage level required to display the logic high level or noise appears on the signal line. When a logic high-level signal appears, the voltage level of the open collector is approximately equal to the working voltage. The difference is due to the voltage drop on the pull-up resistor. This is not necessary if the load is not based on the ground

what is the use of a and B channels

/A and/B channels are the inverse signals of/A and/B channels. This means that when signal a is high, signal/a is low, and when a is low,/a is high. The same applies to any situation with complementary signals. This usually minimizes noise. Some input cards accept both a and/a signals. The two signals are then compared to help eliminate the common mode noise that runs into the wire. The received pulse can be confirmed only when signal a is high level and signal/a is low level. This applies to any channel with complementary signals. Signal a is only an example. This is often referred to as differential output

what is the difference between orthogonality and X4 logic

quadrature output refers to the phase shift of the output signal. When the output signal, signals a and B have a 90 degree difference from each other, this is called quadrature. This is just the explanation of orthogonal nouns. (see what is quadrature output?)

x4 logic refers to how the controller interprets the received signal. This is by converting the edge of each detected a and B channel pulse into its own pulse. This conversion takes place in the controller, not in the encoder

this means that if you order a quadrature encoder with 120 pulses per revolution, the output signals a and B will have a 90 degree phase shift. This does not mean that the encoder will generate 480 pulses per revolution. The increased pulse only occurs in the controller

how to select the number of pulses per revolution (PPR)

when selecting the PPR value of the encoder, please remember some simple rules. Please make sure that the PPR value you choose will not exceed the maximum frequency of the controller or encoder. Try to select PPR close to the value you want to display, so as to eliminate or reduce the need for calibration constants. For example, if you want to display 12 inches per lap, choose PPR of 12. If you want to display 12.00 inches, select 1200ppr. However, don't mistakenly forget the multiplier input by the controller. Most controllers have x2 or X4 logic. If it is x2 logic, it should be obvious. 3. The paper is composed of title, author and work unit, 500 Chinese (English) abstracts, keywords, text, and references, indicating that 12.00 will change to your PPR of 600; When X4 logic changes, PPR is 300. These choices give you only one pulse for each unit you expect

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