To fully understand digital multimeters, it will help if you become clear on the basics of electricity and its parts. After all, these tools always measure some aspect of electricity.
Keep in mind that electricity passing through a conductor is like water flowing through a pipe. Each pipe has force creating a specific pressure, which causes the water to flow. In the case of electricity, that force might be a:
- solar panel
- battery
- generator
- or some other power supply
The pressure made by that power is what we refer to as voltage.
- Voltage is the pressure applied to the circuit.
- Resistance is any restriction to the current’s flow in a conductor.
- Current is the electricity’s flow in the conductor.
Current, resistance, and voltage are the three important components of electricity. Resistance is measured in ohms, current in amps, and voltage in volts.
When you decide to purchase a digital multimeter, it will help if you pay close attention to different things. One of the things you may be thinking about is what those terms digital and count means and the difference between them.
Understanding Display Count in a Multimeter
Keep in mind that the count is the maximum number of digital, which can be displayed on the multimeter’s LCD. In most situations, that value is one less than the display’s count. For instance, the maximum reading per range is one less than 2000 or 1999 if you do have a 2000 count unit.
Here’s another good example for you to get a good comprehension of resolution. Let’s say you are using a ranging unit set on 20 volts, and you measure an application that puts over 20 volts. The display will then read overload or “OL.”
You should reset the multimeter’s dial to a higher range and take another reading. Thus, the most refined reading utilizes the range that offers the best resolution without overloading. Pick the range only higher than the predicted reading.
Remember that the display count is the multimeter’s maximum digital resolution. A 2000 count display has a maximum reading of 1999, which is one less than the display count. On the other hand, a 4000-count display has a maximum reading of 3999.
Such two displays are the most typical; 5000, 20,000, and even 50,000 count displays are accessible as well. The display count identifies the maximum resolution and range.
A 2000 unit is often referred to as the 3 ½ display, as the number three refers to the number of full digits, while the ½ is the capabilities of the most significant digit that could be either 0 or 1. Many digital multimeters these days are 4000 count units.
That only indicates that the most significant would be 0 to 3 or one less than the count of the analog to digital converter.
What is the Importance of Display Count?
The display count is essential in identifying the maximum resolution of the reading. For instance, try to understand the difference when you measure a 240V supply with a 2000 count and a 4000-count digital multimeter. What range would you think you set the meter to?
The 2000 count display would be in the 600V and display 280 volts. The maximum resolution of that is one volt. Moreover, the 4000-count multimeter would be within the 400V range and would have a maximum resolution of .1V. Your unit would show the measurement as 280.0 volts.
It will help if you understand your numerical expressions to correctly read or set up the display of your digital multimeter.
Other Multimeter Specifications You Need to Know About
Apart from display count, you will find other specifications about digital multimeters.
- Accuracy
It’s the biggest allowable error that DMM encounters under particular operating conditions. Mostly, accuracy is displayed as a percentage and shows how close the displayed measurement is to the standard value of the signal measured.
Other applications like specialized industrial equipment, medical aviation, or calibration of cars may need higher accuracy.
- Resolution
Resolution is the smallest increment of change a digital multimeter can detect and display. For instance, a multimeter has a resolution of 1mV in the 3V range. It’s highly possible to notice a change of a 1mV while reading 1V. You can notice voltage adjustments as small as 0.001 value.
- Display Digits
These are used to present the resolution of the digital multimeter. For instance, a 3 ½ meter can show three full digits and a half one. The three full digits show a number from 0 to 9. The half digit shows a one or stays balance. Further, a 4 ½ digit can show four full digital and a half, telling of higher resolution.
- Precision
It refers to the ability of the meter to offer the same measurement recurrently under the same measurement condition. In other cases, if measurements are always repeated, the meter’s precision is very critical to identify an error pattern and compensate for it.
- Range
The resolution and range are connected. Most digital multimeters offer an auto-range function to pick the proper range in measurement. That offers both a relevant reading and an ideal resolution of the measurement.
Remember that many digital multimeters will show OL if the measurement is greater than the set range. The most precise measurement is acquired at the lowest possible range setting without overloading the device.
Final Thoughts
When getting a multimeter for the first time, you need to know what you’re testing, the range you’ll be testing in, and whether or not small values in regard to resolution are critical.
For instance, are you testing a car battery? Then two decimal places at 30V would be ample resolution, so a 4000-count display would be enough. That will offer you a resolution to two decimal places, roughly 39.99V. The same meter can display up to 399.V and 3999V.
Please, don’t be confused between a bigger count for display resolution and the multimeter’s accuracy. They are two different things. One provides the meter’s measurement accuracy, while the other (count) can display that accuracy to the user.
