Digital Caliper

How to Use a Digital Caliper- the "Zero" button features.

2009-02-01T23:26:00.000-08:00

All digital calipers come with "zero" or "origin" button for zeroing the display. This can be done at any point along the slide just by pressing the button. Normally, the zero point is set where the two outside jaws faces are touched with each other. You can also set the zero point at any point along the slide to perform the differential measurement. Below are 3 out of many examples on how a digital caliper can perform measurement by zeroing the display :

1. Measuring the difference in size between objects.

Let say you bought 20 pieces of screws for your assembly project. You need screws with length 6mm or less. The depth of the tapped hole for the screw seems to be very tight, if the screw a bit longer than 6 mm, the screw will not screwed in completely. So you need to measure the length for every piece of the screws you bought before assembling. First, make sure the digital caliper display shows "zero" when you close the jaws completely. Then, pull the jaw so that the digital display shows 6.00 mm.

At this point, push the zero button. The digital display will now shows 0.00 mm.

Now you can measure each of the screws. The display will show the difference of the screw length compare to the dimension you need which is 6mm. Since you need the screw with the same length or shorter, you can only take screws with the display show zero or minus number reading.

The display with plus number reading means the screw is longer than 6 mm. It is also easier to identify how much longer or shorter the screw by using this method.

2. Measuring the center-to-center (pitch) of 2 or more equal size holes.

It will be easier to measure the pitch of the 2 or more equal size holes using a digital caliper. Make sure the holes are the same size by measuring the holes using the internal jaws of the digital caliper. Let say all the holes diameter are measured 6.96 mm.

While measuring one of the hole diameter, when the digital display shows 6.96 mm, hold your thumb lightly, then push the "zero" button. The display will show 0.00 mm.

Then you can use the internal jaws of the digital caliper again to measure the pitch of the 2 holes as shown on the picture. The digital display will show the pitch or center-to-center distance between the 2 holes.

3. Measuring the depth of a small hole.

To measure hole depth, we need to use a digital caliper with probe which attached to the movable head. What if the hole diameter is smaller than the probe? You can not fit in the probe into the hole to measure the depth. What you can do is to find a pin which can fit into the hole to the bottom, and the pin is longer than the hole depth. The pin should not be to loose when fitted into the hole or you may not get accurate measurement. Fit in the pin until the bottom of the hole.

Measure the length of the outside portion of the pin. At that point, set the digital caliper display to zero.

Pull out the pin from the hole. Then measure the overall length of the pin. The digital caliper display will show the dimension of the hole depth.

In this case, the hole depth is 9.62 mm.

How To Use a Digital Caliper

2008-12-16T23:22:00.000-08:00

The main use of a digital caliper is to measure the distance between 2 opposing sides. Please remember to always check for zero point before starting to use your digital caliper.

To check the zero point :
- Make sure the opposing surfaces of the lower jaws which will contact each other are free from any particles or dirt by wiping using clean cloth.

You can also use a clean piece of A4 paper. Put the paper in between the 2 lower jaws. Move the movable head towards the stationery jaw until it touches the A4 paper in between. Apply small force using your thumb so that the paper is pressed between the 2 jaws. Then slowly pull the paper out of the jaws. Do this a few times to make sure the jaws surfaces are clean.

- After the jaws are cleaned, move the movable head towards the stationery jaw so that the two jaws surface completely contact each other.
-Apply small force using your thumb so that the the two jaws do not separate from each other.
- Check the Digital Display for zero reading, push the zero point button to set to zero. Your digital caliper is ready to use.

There are 4 basic type of measurement which a Digital Caliper can perform:

1. External measurement

Using the lower jaws, the external dimension can be measured. Place your workpiece in between the two jaws. Push the movable head towards the workpiece. When both jaws touch the workpiece, hold lightly, make sure the jaws of the digital caliper are perpendicular with the workpiece, then check the digital display for dimension.

2. Internal measurement
Internal measurement can be obtained using the smaller upper jaws. Place the two small upper jaws inside the workpiece to be measured. Pull the movable head so that the two small jaws separate from each other and touch the opposite sides of the measured portion. Make sure the 2 jaws are perpendicular with the hole to be measured. Hold lightly and read the dimension appeared on the digital display.

3. Depth measurement
You can measure the depth of the hole on your workpiece using the probe which is attached to the movable head and slice along the center of the digital caliper body. Depending on the manufacturer, a few digital calipers do not come with this probe. The measurement can be obtained by moving the probe to the lower end of the measured area while the bottom of the digital caliper sitting on the upper end of the measured area. Hold lightly and steadily, make sure that the digital caliper is perpendicular with the workpiece, then take the dimension on the digital display.

4. Step Measurement
As you move the movable head of the digital caliper, notice that at the back of the head, there is a step which also moves. This step can be use to measure step on your workpiece. Put the movable step measuring face of your digital caliper on the upper step of your workpiece and the stationary face of the digital caliper on the lower step of your workpiece to be measured. Make sure the faces of the digital caliper and the step faces are perpendicular with each other. Hold steadily and take the dimension on the digital display.

Why Digital Caliper?

2008-11-13T19:51:00.000-08:00

There are several reasons why you should consider using a Digital Caliper instead of Vernier or Dial Caliper:

1. Cost Effective

A Digital Caliper is not an expansive tool, you can get one for as low as $49.90 to a few hundred dollars depending on the size and maker. For Vernier and Dial Calipers, the prices are not much different from Digital caliper, maybe a bit less. Even though a battery is used to power up the digital caliper, the battery life is very long. Some of the digital calipers come with battery power-conserving design permitting 3 - 5 years (20,000 hours) continuous operation with a single battery. With more advantages compare to other types of caliper, the Digital Caliper is worth buying.

2. Reading your measurement is easy

All you need to do is measure your workpiece, then the measurement is there on the large electronic digital display on your digital caliper, saving you from reading and deciphering the measurement from a printed scale or dial yourself. This means that you can reduce the chances of reading error. (But, please remember to always check your zero point whenever you want to start using your digital caliper.) Since you can take measurement just by reading the number on the digital display, this digital caliper is suitable to be used in the area where visibility is restricted. And, some of the digital calipers contain a "reading hold" feature, allowing to hold the reading for later view, when the caliper is used in locations where the display can not be seen.

3. Digital Caliper has high accuracy

Most of the digital calipers have the accuracy of +/-0.02mm or +/-0.0008". I have been working at a precision machine shop for 10 years. We use CNC turnings and CNC machining centers to produce our precision parts. Digital caliper is the main measuring instruments we used at our factory. Many of our jobs require tolerance of +/-0.05 mm and above, and this is just perfect task for a digital caliper. Of course for a more precise measurement (eg. +0/-0.017 mm) we must use micrometer or digital micrometer. With Vernier caliper it is almost impossible to measure your workpiece with tolerance +/-0.05 mm.

4. Digital Caliper has many advance features

Many of the digital calipers today have a conversion button which can switch between metric and imperial unit. With this feature you can easily convert your measurements from millimeter to inch or the other way around just by pushing a button.

A digital caliper display can be set to zero at any point along the slide, which will enable differential measurement. Differential measurement is the measuring of the difference in sizes between 2 measurement points. Using a digital caliper, you can automatically calculate the difference, saving you from manually calculate using calculator.

Some digital calipers come with data output connection which allow them to be interfaced with a personal computer. You can use spreadsheets or other similar software to instantly store the measurements taken. This will reduce the time taken to manually record the series of dimensions as for preparing your inspection report.

Digital Caliper- What is a Digital caliper?

2008-11-07T05:41:00.000-08:00

A digital caliper comes with an electronic digital display on which the reading is displayed. Some digital calipers can be switched between metric and inch units. All provide for zeroing the display at any point along the slide, allowing the same sort of differential measurements as with the dial caliper but without the need to read numbers that may be upside down. Digital calipers may contain some sort of "reading hold" feature, allowing the reading of dimensions even in awkward locations where the display cannot be seen.

With all of these benefits, digital calipers have by no means replaced the dial caliper. Digital calipers typically do not have the beam structure of a dial or vernier caliper and therefore do not have the repeatability or accuracy to an amateur user.

Increasingly, digital calipers offer a serial data output to allow them to be interfaced with a personal computer. This means measurements can be taken and instantly stored in a spreadsheet or similar piece of software, significantly decreasing the time taken to take and record a series of measurements. The output of non-name brand calipers is usually 24 bit 90 kHz synchronous. A suitable interface to convert the output to RS-232 levels and format can be built or purchased.

Like dial calipers, the slide of a digital caliper can usually be locked using a lever or thumb-screw.

Both dial and digital calipers can be used with accessories that extend their usefulness. Examples are a base that extends their usefulness as a depth gauge and a jaw attachment that allows measuring the center distance between holes.

Digital calipers contain a linear encoder. A pattern of bars is etched directly on the Printed circuit board in the slider. Under the scale of the caliper another printed circuit board also contains an etched pattern of lines. The combination of these printed circuit boards forms two variable Capacitors. As the slider moves the capacitance changes in a linear fashion and in a repeating pattern. The two capacitances are out of phase. The circuitry built into the slider counts the bars as the slider moves and does a linear interpolation based on the magnitudes of the capacitors to find the precise position of the slider.

Article source : http://en.wikipedia.org/wiki/Caliper