Can a dial indicator read negative values? This question may seem simple, but it actually involves an understanding
of the measurement principle of the micrometer. Let's delve deeper into the measurement range and usage limitations
of the micrometer.
I. The Principle of Reading a Dial Indicator: The Secret Behind the Pointer
1. A dial indicator uses a gear transmission mechanism to magnify the tiny displacement of the measuring rod
and indicates it on the scale through the pointer. This enables precise measurement. The direction and magnitude
of the pointer's deflection represent the movement direction and displacement of the measuring rod.
2. The scale dial of a standard micrometer usually starts from zero. The pointer moving to the right indicates
a positive value, while the pointer moving to the left indicates a negative value.
3. Therefore, from the perspective of the deflection direction of the pointer, the dial indicator can read negative values.
II. Measurement Range: The "operating area" of the pointer
1. The measurement range of a dial indicator is determined by its scale. Common dial indicators have different
ranges such as 0-10mm and 0-25mm. The pointer can only deflect within its scale range; beyond this range,
no reading can be obtained.
2. Some dial indicators have a preload function, which allows the pointer to be preset at a non-zero position,
such as at 5mm. This enables an expanded measurement range. For example, if the range is 0-10mm and a preload
of 5mm is applied, the measurement range becomes -5mm to +5mm.
3. Therefore, whether a micrometer can display negative values depends on its initial setting and measurement range.
III. Usage Restrictions
Even pointers may encounter situations where they are unable to perform their function properly.
1. Exceeding the Measurement Range: If the displacement of the measuring rod exceeds the measurement range
of the dial indicator, the pointer may get stuck or be damaged. Therefore, it is essential to avoid using beyond
the measurement range.
2. Severe Impact: The internal mechanism of the dial indicator consists of precise gear transmission components.
Severe impacts can cause damage to the gears, thereby affecting the measurement accuracy.
3. Temperature variation: Temperature changes can affect the accuracy of the dial indicator.
Therefore, when conducting precise measurements, one should be aware of the impact of temperature.
IV. Practical Applications of Negative Numbers: "Reverse Indication" of Indicators
1. Baseline Measurement: Set a reference value. Readings above the reference value are considered positive,
while readings below the reference value are considered negative.
2. Measurement of workpiece size deviation: Set the standard size as zero. Positive values indicate that the size is out
of tolerance, while negative values indicate that the size is insufficient.
V. Other types of micrometers: Expand your "measurement toolkit"
1. Lever micrometer: Utilizes the principle of leverage to magnify the displacement of the measuring rod,
suitable for measuring very small displacements.
2. Digital Micrometer: Converts the pointer reading into digital display, making it easier to read and record data.
Here are the questions you might be interested in and their answers:
Q: What is the accuracy of the micrometer?
A: The common accuracy of a micrometer is 0.01mm.
Q: How to calibrate a dial indicator?
A: Calibration can be performed using standard block gauges.
Q: What should be noted when using a micrometer?
A: Handle with care, avoid collisions and impacts, and keep clean.
The structural design of the dial indicator itself determines that it can read negative values.
However, whether it can read negative values and how to read them depend on the specific measurement
requirements and settings.
