Many times we come across terms, ‘abc’ Multimeter is 3 ½, 4 ½, 6 ½, 7 ½ digits or 2000, 4000, 6000 counts. (‘abc’ means the manufacturer of multimeter)

We also come across the accuracy of ‘abc’ Multimeter is ‘0.15% + 2 digit’.

While buying Multimeter Digits and Counts is an important factor

**What do these counts and digits mean?**

Digits and counts are two different ways to express the same thing.

## Multimeter Digits

Take an e.g. of 3 ½ digit Multimeter.

The format is given as a whole number followed by a fraction, usually a 1/2 or a 3/4.

The whole number represents how many digits displayed from 0 to 9.

The fraction is ½ or a ¾.

Fraction ½ means the most significant digit for each range can be 0 or 1.

A ¾ means the most significant digit for each range is greater than 1.

3 ½ digit Multimeter can display three complete digits and one ½ digit. Three complete digits can have any numbers from 0 to 9 and one ½ digit can have only 0 or 1.

Three Positions of digits can display 0 to 9 numbers and leftmost position can only display 0 or 1 number in 3 ½ digit Multimeter.

Similarly for 4 ½,6 ½, 7 ½ digit Multimeter displays complete 0 to 9 numbers on four, six ,seven positions respectively and leftmost position displays only 0 or 1 number.

An illustration for 3 ½ Digit Multimeter Display (shown below)

A 6 ½ Digit Multimeter Display (as shown below)

A 7 ½ Digit Multimeter Display (as shown below)

An 8 ½ Digit Multimeter Display (as shown below)

## Multimeter Counts

If the display of Multimeter is 2000 counts. It can display digits from 0000 to 1999 counts. i.e. 3 ½ digit Multimeter.

If the display of Multimeter is 20000 counts. It can display digits from 00000 to 19999 counts. i.e. 4 ½ digit Multimeter.

Therefore, Digits and counts are two different ways to express same thing.

Counts are ignoring any decimal points and polarity signs.

Many newer Multimeters don’t have a restriction of 0 or 1 at leftmost digits.

**Example**

Display of Multimeter is 4000 counts. It can display digits from 0000 to 3999 counts. I.e. leftmost digit can have 0,1,2,3 digits.

So, it is more practical to describe a Multimeter by its counts rather than digits.

Counts tell you what the instrument can display before it changes to the next range.

For example, suppose a Multimeter is of 20000 counts (4 ½ digit Multimeter). This means the range changes when it hits 20000 on display.

A 20000 count meter can read 19.999 V on the display, but when it tries to display 20 V, it will read 020.00 V instead or simply 20.00 V.

The Multimeter moves to the next range mean one digit of resolution is lost.

Generally 2000 Count Multimeter (3 ½ digit Multimeter) have range 200.0 mV, 2.000 V, 20.00 V, 200.0 V.

Generally 6000 Count Multimeter have range 600.0 mV, 6.000 V, 60.00 V, 600.0 V

The count refers to the limit of the highest value the Multimeter will display for each range.

As soon as a measured value reaches this limit, the range will move up and the resolution will be downgraded by a factor of 10, that is, the decimal place will be moved to the right one spot.

If we had a Multimeter that was designed to measure up to 1000V with a 40000 count, then, the ranges and resolution can be as follows:

0.0000 to 3.9999 with a resolution of 0.0001

4.000 to 39.999 with a resolution of 0.001

40.00 to 399.99 with a resolution of 0.01

400.0 to 1000.0 with a resolution of 0.1

## Accuracy

The accuracy of Multimeter is written as “0.15% + 2 digits”

Means 0.15 % of indicated value + 2 × Resolution

**Example**

Reading of Multimeter at 1 volt is 1.005 V

Resolution is 0.001 V

Accuracy = (0.15% × 1.005) + (2× 0.001)

Accuracy = 0.0035 V

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Accuracy = (0.15% × 1.005) + (2× 0.001)

Accuracy = 0.0035 V

Shouldn’t that be 0.0034V?

Well explained with the help of examples.

Good explanation. Helpful in clearing the basics.

Thank You..