How to Choose a Multimeter? [CAT Ratings]
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The key to selecting the right multimeter is going for the safest device possible and defining what options you will need. Multimeter with instructions in Chinese may do a good job, but we are dealing with electricity here and if the device ends up not being very safe, you will be sorry in the end.
In this article, I will be talking about digital multimeters since they are the most commonly used (analog multimeters are also available if anyone is interested).
First of all, a multimeter is a device that can give you several different readings (as long as you change a setting):
- Voltmeter. Voltage measurement (“V”).
- Ammeter. Current measurement (“A” or “I”).
- Ohmmeter. Resistance measurement (“Ω”).
- Continuity. Measurement for electrical connection (“sound icon”). This one also comes with a beeping sound (no beep – circuit is broken).
These are the four basic things that you will need if you are not a professional electrician. Also, professionals most commonly use the version of a multimeter with a clamp, but for regular home use, this is not very necessary.
So, how do you choose a multimeter that suits your needs?
- Step 1. Choose the right category. Please note that test leads that come with your multimeter could be a different category. Choose your leads of equal and higher Cat rating (which is your safety standard).
- Step 2. Choose the desired voltage value. Make sure your leads are equal or higher voltage rating than a multimeter. You should also check if your multimeter comes with a fuse for added protection.
- Step 3. Make sure your multimeter is supplied with a protective tip. It adds to the category (or protection) rating.
- Step 4. Go for quality. Multimeter and its test leads should be UL-listed.
- Step 5. Choose needed and desired settings. For general DIY use, you may want to have: Volts AC (∼ ), Volts DC (⎓), Amperage (μ or A), Ohms (Ω), Continuity ( or a sound symbol).
Here is a nice guide on choosing multimeters:
Other features you may want to be looking for:
- TRMS (or True RMS). Unless you are trying to display a value of pure sine wave, paying a little extra for True RMS is highly recommended. It will be more accurate on non-linear AC loads.
- Display Count (Resolution). This is a decimal count and the larger the number, the more digits after decimal will be included (therefore making your reading more accurate). More expensive multimeters tend to have higher count ratings.
- Ranging (Automatic or Manual). Autoranging is the simplest form of detecting the range of your electrical component. It is very popular among people who don’t want to think about which range to select.
- Other interesting features. More advanced models may include the ability to do a diode test, have a “NO-contact” voltage detection, and even supply you with an infrared camera!
Don’t forget to check the maximum current and voltage rating of your multimeter to make sure it can handle your load.
A voltage rating means how much your multimeter can withstand before blowing a fuse (assuming there is a fuse inside).
There is also a safety standard called CAT (meow!) and no, this is not a regular cat, but a rating of the latest UL standard (UL 61010B-1). Here is a general breakdown:
|CAT I||Up to 800V||Telecommunications and electronics|
|CAT II||Local-level of circuits||Most lighting equipment and appliances|
|CAT III||Distribution circuits||Feeders or branch circuits|
|CAT IV||Primary supply source||Power lines|
** Warning! Before using your multimeter on something, make sure that it can handle that particular power source! Do NOT use larger fuses than installed by the manufacturer in order to avoid making a bomb out of your multimeter!
You can divide multimeters into the following categories:
- Simple under $25 (paid link). Simple cheap multimeters that would normally work for an average home user.
- Basic $26 – $50 range (paid link). These higher-end simple multimeters have more features and a higher CAT rating.
- Advanced $51 – $100 range (paid link). These multimeters would work if you are just starting your career as an electrician or HVAC technician.
- Professional $101 – $200 range(paid link). These devices are also more accurate than the cheaper versions and can handle a higher amount of current. Perfect for electricians, HVAC technicians, auto repairmen.
- SuperPro $201 and up (paid link). Well, these guys know what they are paying for! Multimeters in this price range have more features than we (regular human beings) can possibly comprehend!
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