Hysteresis in Sensors: Meaning, Interpretation, and Correct Option

In sensor terminology, hysteresis means that the output for a given input depends on the previous input path, not just the present value.2 In practical measurement systems, if the input is increased to a certain value and then later decreased back to that same value, the sensor may produce two slightly different outputs.2

Therefore, the correct interpretation is:

(ii) Difference in output when input increases vs. decreases.2

This is a classic static performance error in instrumentation and is distinct from dead time, dead band, and random noise.2

A simple conceptual view is:

Mathematically, if the same input $x$ is reached from two directions, hysteresis implies:

$$H(x) = y_{\uparrow}(x) - y_{\downarrow}(x)$$

where $y_{\uparrow}(x)$ is the output during increasing input and $y_{\downarrow}(x)$ is the output during decreasing input.2

Footnotes

1. Hysteresis in pressure calibration: What you need to know - Explains hysteresis as differing readings at the same pressure during increasing and decreasing cycles. ↩ ↩²

2. Hysteresis - SensorsONE - Defines hysteresis as the difference between measurements at the same point taken during increasing and decreasing values. ↩ ↩² ↩³

3. Hysteresis 101 - Interface - Describes hysteresis for force sensors as the algebraic difference in output for ascending versus descending loading. ↩ ↩² ↩³

4. Calibration Error Hysteresis Non-linearity Saturation Dead Band (PDF) - Distinguishes hysteresis from dead band, response time, repeatability, and other sensor characteristics. ↩

5. Sensor Resolution vs Accuracy vs Repeatability - FUTEK - Explains how hysteresis differs from repeatability and contributes to sensor accuracy specifications. ↩

Why option (ii) is correct

In instrumentation, hysteresis is commonly defined as the difference between two measurements taken at the same input point: one while the input is being increased and the other while it is being decreased. This behavior appears because many sensing elements have a form of memory effect, often caused by internal friction, elastic recovery limits, magnetic effects, or material deformation.2

For example, in pressure calibration, a sensor might read 49.95 kPa when pressure rises to 50 kPa, but 50.05 kPa when pressure falls back to 50 kPa. The input is the same, yet the output differs because the sensor follows different ascending and descending paths.2

This means hysteresis is not merely about delay in time; it is fundamentally about path-dependent output.2

Footnotes

1. Hysteresis - SensorsONE - Defines hysteresis as the difference between measurements at the same point taken during increasing and decreasing values. ↩

2. Hysteresis in pressure calibration: What you need to know - Explains hysteresis as differing readings at the same pressure during increasing and decreasing cycles. ↩ ↩² ↩³ ↩⁴

3. Hysteresis 101 - Interface - Describes hysteresis for force sensors as the algebraic difference in output for ascending versus descending loading. ↩ ↩²

4. Hysteresis - Wikipedia - Provides broader background on hysteresis as history-dependent behavior and distinguishes it from simple dynamic lag. ↩

Distinguishing hysteresis from related sensor errors

Several measurement concepts are frequently confused with hysteresis:

A useful mental model is that hysteresis forms a loop between the loading and unloading curves.2

Footnotes

1. Calibration Error Hysteresis Non-linearity Saturation Dead Band (PDF) - Distinguishes hysteresis from dead band, response time, repeatability, and other sensor characteristics. ↩ ↩² ↩³ ↩⁴

2. Hysteresis in pressure calibration: What you need to know - Explains hysteresis as differing readings at the same pressure during increasing and decreasing cycles. ↩ ↩²

3. Sensor Resolution vs Accuracy vs Repeatability - FUTEK - Explains how hysteresis differs from repeatability and contributes to sensor accuracy specifications. ↩ ↩²

4. Hysteresis - Wikipedia - Provides broader background on hysteresis as history-dependent behavior and distinguishes it from simple dynamic lag. ↩

Applied example

Consider a force sensor tested at 50% of full-scale load. During loading, the output is recorded as one value; during unloading, the output at that same 50% load is slightly different. That difference is the hysteresis error. In engineering specifications, hysteresis is often reported as a percentage of full scale, since it contributes directly to overall measurement uncertainty.2

For multiple-choice interpretation, this lets us reject the distractors systematically:

• (i) refers to dynamic lag or response delay, not the standard sensor-specification definition.2
• (iii) implies no response to changing input, which is closer to dead band or saturation.
• (iv) implies random fluctuations, which is noise or instability.2

So, in formal instrumentation language, hysteresis means the difference in output when the same input is reached from increasing and decreasing directions.3

Footnotes

1. Hysteresis 101 - Interface - Describes hysteresis for force sensors as the algebraic difference in output for ascending versus descending loading. ↩ ↩² ↩³

2. Sensor Resolution vs Accuracy vs Repeatability - FUTEK - Explains how hysteresis differs from repeatability and contributes to sensor accuracy specifications. ↩ ↩²

3. Calibration Error Hysteresis Non-linearity Saturation Dead Band (PDF) - Distinguishes hysteresis from dead band, response time, repeatability, and other sensor characteristics. ↩ ↩² ↩³

4. Hysteresis - Wikipedia - Provides broader background on hysteresis as history-dependent behavior and distinguishes it from simple dynamic lag. ↩

5. Hysteresis in pressure calibration: What you need to know - Explains hysteresis as differing readings at the same pressure during increasing and decreasing cycles. ↩

6. Hysteresis - SensorsONE - Defines hysteresis as the difference between measurements at the same point taken during increasing and decreasing values. ↩