BANNER BES58-6 series incremental encoder selection and troubleshooting guide

BANNER BES58-6 series incremental encoder selection and on-site troubleshooting complete guide

In the field of industrial automation, rotary encoders are the core feedback components for measuring angles, positions, and speeds. The reliability of the encoder directly determines the operational quality of the entire system, from the speed control of the servo motor to the position limitation of the crane. However, facing the dazzling array of encoder models on the market (NPN, push-pull, line drive HTL、TTL……）， As well as common faults such as signal loss, counting errors, and mechanical damage on site, many maintenance engineers are confused. This article will take a typical industrial incremental encoder (referring to the 6N/6H/6T/72T series) as an example to provide you with a full process practical guide from selection, installation to fault diagnosis.

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Incremental Encoder Core Selection: Output Type and Electrical Matching

Choosing the wrong output type of encoder is one of the most common errors on site. Different controllers and counters require different signal interfaces. Let's analyze the four mainstream output methods one by one.

1. NPN open collector output (model suffix 6N)

Electrical characteristics: The emitter of the output transistor is grounded and the collector is open circuit. An external pull-up resistor is required to obtain a high-level signal.

Applicable scenarios: Early Japanese PLCs or counters, with a common anode input circuit (receiving low level valid). The power supply voltage range is wide (10-30VDC), the maximum driving current per channel is 30mA, the maximum output frequency is 100kHz, and the rise time is about 1 microsecond.

Fault tendency: If the pull-up resistor is not installed correctly, the signal will always be at a low level, causing abnormal counting. In addition, the anti-interference ability is weak during long-distance transmission.

2. Push Pull output (model suffix 6H)

Electrical features: It contains a pair of complementary transistors that can output both high and low levels without the need for external pull-up resistors.

Applicable scenarios: Compatible with most controllers with NPN and PNP inputs, it is an ideal choice for universal replacement. It also supports 10-30VDC power supply, with a frequency of 100kHz and a rise time of 1 microsecond.

Advantages: Strong signal driving capability, suitable for medium distance transmission (tens of meters). In the renovation of old equipment, if the output type of the original encoder is uncertain, push-pull output is usually a safe choice.

3. HTL output (High Threshold Logic, model suffix 6T)

Electrical characteristics: High threshold logic, usually output signal amplitude is the same as the supply voltage (10-30V), with stronger anti-interference ability. This model 6T provides 6 signals (A, A -, B, B -, Z -), namely differential output.

Applicable scenarios: applications with harsh industrial environments and long cable distances (up to 100 meters or more). Differential signals (A and A -) are transmitted through twisted pair cables, and common mode interference can be effectively suppressed.

Parameters: Power supply 10-30VDC, maximum no-load current of 150mA (higher than the previous two, please pay attention to power capacity), rise time of only 100 nanoseconds, much faster than NPN/push-pull.

4. TTL output (Transistor Transformer Logic, model suffix 72T)

Electrical features: Fixed 5V power supply, differential output (RS-422 compatible). The signal amplitude is usually 5V and the rise time is 100 nanoseconds.

Applicable scenarios: Connecting high-speed counters, servo drives, or motion control cards. Due to low voltage, it is not suitable for long-distance transmission (recommended to be less than 10 meters). Six signal lines (A, A -, B -, Z -) provide extremely high noise resistance performance.

Attention: Never connect 24V power supply, otherwise the output stage will be immediately burned out.

On site selection checklist

Recommended input type for controller, maximum distance for encoder output power supply

Common anode (low level effective) NPN (6N) 10-30V<30m

Common cathode (high level effective) or unknown push-pull (6H) 10-30V<50m

HTL differential (6T) 10-30V 100m for long-distance and strong interference scenarios+

5V TTL differential interface TTL differential (72T) 5V<10m

Mechanical specifications and installation points: Avoid physical damage

The mechanical lifespan and reliability of encoders largely depend on whether they are installed correctly. According to the provided mechanical specification table:

Speed limit: Maximum 6000 revolutions per minute. Exceeding this speed may cause the bearing to overheat or the photoelectric encoder to shatter.

Axle load: maximum axial load of 40N, maximum radial load of 20N. This means that it is not allowed to use hammering to install the coupling, nor is it allowed for the pulley to be too tight. Excessive radial load is the primary cause of premature damage to encoder bearings.

Starting torque: 5 × 10 ⁻⁷ N · m, very small, only needs to overcome bearing friction and sealing resistance. This implies that the encoder cannot be rigidly connected to the motor shaft and a flexible coupling must be used.