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Virtual Dial Indicator, Simulator in Hundredths of Millimeter

Relógio comparador - Dial Indicator - Reloj Comparador
Simulator of reading and understanding of Dial Indicator or Dial Gauge - how to use, reading and understanding this instrument of linear measurement

The Dial Indicator, some times called Prob Indicator, it is one of the few analog measurement instruments that allows the measurement of linear measurements directly (by measuring directly the desired) or indirectly (establishing the difference between the desired measurement and another known).

In this simulation you will learn the science of using this measuring instrument, interacting with the spindle or the contact tip ( see main components). In this learning object, you can also turn the ‘display’ (dragging and dropping the hoop in a circular motion) so that the line ‘zero’ align with the pointer after the called ‘ preload ‘, hide the measure provided (by clicking the eye icon) and cancel the spring effect of the instrument (by clicking the ‘lock’).

Dial Indicator or Dial Gauge and their utilization

This measuring instrument operates affixed to devices such as bases, supports, performances or guides. Due to its fragility, its use in the operator’s hand is discouraged.

Dial Indicator and the direct measurement (indicator)

By definition, direct measurement (or indicator) occurs when the value of the wished measurement (mensuring it) is read directly in the device display of the measurement instrument. For example, when we determine a linear dimension with a paquimeter ( see the paquimeter simulator ), the reading that we obtained in the scale and it’s vernier , not considering errors, is the efective measure of the object that we are submiting to measurement.

We use this dial indicator on this mode of measurement together with surface plate and(or) supports to measure the thick plates, for example, among other measures relatively small.

This method of utilization is seen in the Simulator and on figure 1. We submitted the instrument to a preload , set to zero mark (turning the counter), we moved the spindle manually giving space to put the object to be measured in the axis of the instrument and return the spindle until the contact with the part that holds it. The dimension is read directly in the counter, by relative position (displacement) of the main pointer and of the turns counter.

Dial Indicator and the indirect measurement

On this case, by contrast, we have indirect measurement (indicator), when the read value in the display device of the instrument it is not the value of the measure that we are measuring. For example: when we use a barometer, or we measure the shadow, to determine the height of a building.

One of the possible uses of the dial clock compartator is to calculate the difference between a pattern and the one of we are measuring.

Dimension of part = pattern dimension + (or) – value read in the instrument

We zero the instrument with a standard whose dimension we know and establish the difference between it and that of the object we are subjecting to measurement, algebraically-Figure 2.

Dial Indicator and the mechanic of its reading

Using a dial indicator is one of the easiest tasks in metrology. Let’s understand this method using the simulator as an example and you will be able to use several other models, with their scales, scopes and resolutions. In general, they come with a ‘hint’ printed on the display saying their resolution and nominal range (ex: 0.01 – 10.00 mm or 0.001 – 1,000 “). (To interact with the Milesimal Inch (1,000 “) Comparator Clock Simulator click here)

A full turn of our simulator’s main pointer represents the equivalent of one millimeter of spindle motion. Its dial has ten divisions numbered (from 0 to 90 from ten in ten) and each of them is subdivided by ten, making a hundred (100) divisions. In this way, each of the marks on the display equals one-hundredth of the millimeter (0.01mm) -figure 1. The nominal range of the instrument of Figures 1 and 2 is 10mm (to circumvent the limitations imposed by the resolution of the monitors, the nominal range Of this Comparator Clock Simulator is 1.14mm – Click here and interact with a realistic comparator clock simulator with a realistic 10mm nominal range); This feature makes it necessary for some device to count the number of turns of the main pointer (number of whole millimeters to be added to the centesimal part).

Procedure to direct reading

figure 1 – dial indicator – direct measure

  • This step by step describes the procedures to the reading of figure 1. Observe that the pointers are turning to opposite directions and the movement of the main pointer is clockwise;
  • The instrument is fixed in a place that works in conjunct with a surface plate.
  • Touch the contact point to the surface plate and apply the preload.
  • Turn the display until the mark with the zero (0) mark is aligned with the pointer.
  • Read the initial condition of the pointers, comparing with the display.
  • Gently, raise the spindle until you find space for the object of measurement.
  • With the same care, return the spindle (propelled by a spring) until it touches the object of the measurement.
  • Read the pointer of the turn counter (small display), subtracting the number of spaces between the marks that it runned into.
  • 7-0 = 7mm
  • See that the pointer was perfectly aligned with zero at the beggining and later passed the seventh line. That means that there is a centesimal part to be read.
  • Read the main pointer to determine the centesimals.
  • It passed through seven numbered lines (0.1mm each) and a small line when went away from zero and stopped in the last turn, like this: 7×0.1mm + 1×0.01mm = 0.71mm
  • Add the results
  • 7mm + 0.71mm = 7.71mm, that is the dimension of teh object that is being measured.

Procedures for indirect reading

figure 2 – dial indicator – indirect measure

This step by step describes the procedure for reading figure 2. Observe that the pointers are counter-rotating and the movement of the main one is anti-clockwise. Do not forget that for indirect readings:

Dimension of the part =
Pattern dimension + (or) – Value read in the instrument

  • The instrument is fixed in a place that works in conjunction with a surface plate.
  • Touch the contact point in the surface plate and set the preload.
  • Turn the display until the mark with the zero (0) mark aligns with the pointer.
  • Read the initial condition of the pointers.
  • Gently.
  • Raise the spindle.
  • Take off the pattern and put in the object for measurement.
  • With the same care, return the spindle until it touches the object of the measurement.
  • Read the pointer of the turning counter, subtracting the number of spaces between the ones that passed through.
  • 10-8 (the pointer moved in the opposite direction of the counter) = 2mm
  • Read the main pointer to determine the centesimals.
  • It passed through two numbered lines (0.1mm each) and nine small lines when started from zero and stopped in the last turn, like this: 2×0.1mm + 1×0.09mm = 0.29mm
  • Another way to read this thing is: 100/100-70/100 = 30/100+1/100 = 0.29mm
    See that he swept the tenths in the opposite direction of the count, so use (-), however, the pointer has not reached 70 cents, missing a hundredth, hence add (+) 1/100
  • Add the results
  • 2mm + 0.29mm = 2.29mm
  • Subtract this result from the value of the measured dimension of the pattern (the direction of rotation of the (counterrotating) pointers indicates that the object is smaller than the standard.
  • 10mm – 2.29mm = 7.71mm

figure 3 – dial indicator – aligning zero of the display

Turning display to zero mark

Once the preload has been established, the dial indicator has a ring that allows you to rotate the dial to, for example, align the zero with the Main Pointer for easier reading, for this you should loosen the Ring Fixing Screw.

Dial Indicator Components

Click here to explore a image of a dial indicator and know the name of its main components.
After interacting with the virtual dial indicator, I recommend that you solve this:
List of exercises of reading and interpretation of the dial indicator in millimeter in centesimal resolution (0.01mm)

Virtual Dial Indicator: Simulator of use, reading and interpretation of the Dial indicator

In the Dial Indicator below, drag and drop, in the vertical, the orange highlighted detail for reading

Tips:
– turn the bigger display of the dial indicator
– click in the icon ‘eye’ to hide the measure
– click in the icon ‘locker’ to cancel the effect of the spring of the instrument

note: by limitations imposed by the resolution of the monitor, the distance ran by the the contact tip is not proportional to the indicated measure

Eduardo Stefanelli

Engenheiro por profissão, professor por vocação

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