When purchasing absolute value encoders, these three parameters can easily lead to unnecessary expenses

[Core Summary] When purchasing absolute value encoders, the three major cost components are single-turn vs. multi-turn, interface protocol, and resolution. Don't be misled by the parameter list. Before purchasing, calculate the actual on-site usage first, and then discuss model selection. This can help avoid unnecessary expenses.

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1. Determine the number of turns and the interface first, then we can discuss other matters

Whether it's a single turn or multiple turns, it depends on whether the shaft rotates completely around one circle

The shaft does not rotate a full circle within one stroke; a single rotation is sufficient. If cumulative positions over multiple rotations need to be recorded (such as in winding or lifting mechanisms), then multiple rotations are required. Multiple rotations are achieved through gear sets or internal counting. The greater the number of rotations indicated, the more complex the structure and the higher the cost. Rotations that are not needed on-site are a waste of money.

When it comes to interface protocols, what matters is the controller, not which one is "advanced"

The FNC series commonly includes four types: SSI, BISS, Profibus, and CANopen. SSI stands for Simple Serial Interface, while BISS boasts high speed and strong anti-interference capabilities. Profibus and CANopen are fieldbus protocols. When selecting a model, it's crucial to first clarify which type is supported by the host computer. If the model doesn't match, a conversion module will be required, incurring significant hidden costs.

II. A high resolution does not necessarily mean it is usable

This is a common premium point in the industry. Suppliers tend to set the resolution per circle to a very high number, but the on-site mechanical accuracy and controller sampling simply cannot handle it. A resolution of 13 bits per rotation is sufficient; forcing it to 16 bits results in a significant price difference, yet there is no perceptible difference in positional accuracy.

The resolution should be inversely derived based on "how many code values correspond to the minimum displacement of the mechanism", leaving a reasonable margin. Don't be fooled by the attractive numbers on the parameter table.

III. Protection, shaft diameter, and temperature are minor factors that lead to repair requests

When evaluating protection levels, it is important to consider not only the IP number

IP67 does not guarantee long-term immersion in oil or resistance to high-pressure washing. It depends on actual testing conditions: dust concentration, whether there is spraying, and the presence of metal shavings. When selecting a model, it is safer to provide the supplier with photos of the on-site environment for confirmation, rather than blindly trusting the specification sheet.

The shaft diameter does not align with the flange, and the cost of mechanical modification is higher than that of the encoder

The solid shaft/hollow shaft and flange model (such as clamping flange, synchronous flange) must be consistent with the original equipment. A mistake in purchasing can either require reprocessing of the coupling or modification of the mounting base, resulting in downtime costs far exceeding the price difference of the encoder.

IV. Full Life Cycle: Spare Parts, Calibration, and Warranty Are the Hidden Costs

The arrival of the goods is just the beginning. It is important to inquire about the length of the warranty period [please verify], the maintenance cycle after the warranty expires, and whether there is long-term supply of the same model (to avoid stockouts after three years of production line use). Absolute value encoders rely on internal mechanisms to maintain their position in case of power loss, and for battery-powered models, the replacement frequency needs to be calculated [please verify].

It is recommended to include the "total cost of ownership over three years" in the price comparison during procurement, rather than just comparing individual unit prices.

[Parameter Table]

Key Terms

What should a purchaser verify

Pitfalls to Avoid

Note:

Single lap/multiple laps

Whether the actual number of revolutions exceeds one circle requires accumulation over several circles

Marking multiple circles on the product is a waste of money

Number of multi-turns [please verify]

Interface protocol

Which of SSI/BISS/Profibus/CANopen is supported by the host computer

Interface mismatch and conversion module

Confirm bus model [Please verify]

Resolution ratio

Infer the required number of bits based on the minimum displacement

High-digit numbers do not require pure premium

Single-turn/multi-turn resolution [Please verify]

Protection level

Real-world conditions of dust, spray, and oil mist

Misjudgment based solely on IP numbers

Suggested IP rating [please verify]

Shaft diameter/flange

Solid/hollow shafts and flange specifications are consistent

Unable to install the modified machinery, resulting in high downtime costs

Shaft diameter [please verify]

Operating temperature

On-site high and low temperature, temperature drift requirements

Narrow nominal range leads to early failure

Temperature range [please verify]

Quality Assurance and Supply

Warranty period, maintenance cycle, and long-term supply

Risk of stock-outs and production discontinuation

Warranty period [please verify]