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I’ve been testing three popular FNIRSI multimeters — the DMT-99, the DMC-100 clamp meter, and the S1 — to figure out which one actually belongs in your home toolkit. All three pack 9999-count True RMS measurement, but they go about it in very different ways.
This comparison is for the DIYer or hobbyist who wants a reliable, rechargeable meter without paying pro-level prices. The big trade-off here is between the DMC-100’s clamp jaw for measuring current and the DMT-99’s fancy recording features. Let me break down what I found so you can pick the right one.
🏆 Quick Picks — My Top Recommendations
Best Overall: FNIRSI DMT-99
Best for home use with a 2.4-inch color screen and unique recording/monitoring modes — Check Price →
Runner-Up: FNIRSI DMC-100
Best for measuring AC current up to 600A with its clamp jaw and temperature probe — Check Price →
Best Budget: FNIRSI S1
Most compact and lightweight option with a built-in electric pen design and NCV detection — Check Price →
I’ve laid out the most important specs side-by-side so you can see exactly how the DMT-99, DMC-100, and S1 stack up against each other.
Full Specs Comparison
| Specification | FNIRSI DMT-99 Digital Mul | FNIRSI DMC-100 Digital Cl | FNIRSI S1 Smart Digital M |
|---|---|---|---|
| Counts | ✅ 9999 | 9999 | 9999 |
| Measurement Type | Ammeter, Multimeter, Ohmmeter, Voltmeter | Ammeter, Multimeter, Ohmmeter, Voltmeter | — |
| Power Source | Battery Powered | Battery Powered | — |
| Weight | ✅ 0.42 Pounds | — | — |
| Color | Black and Blue | Black | — |
| AC/DC Voltage | ✅ Yes | ✅ Yes | ✅ Yes |
| AC/DC Current | — | ✅ 600 A | — |
| Resistance | ✅ Yes | ✅ Yes | ✅ Yes |
| Capacitance | ✅ Yes | ✅ Yes | ✅ Yes |
| Diode Test | ✅ Yes | ✅ Yes | ✅ Yes |
| Frequency | ✅ Yes | ✅ Yes | — |
| NCV Detection | ✅ Yes | ✅ Yes | ✅ Yes |
| Recording Mode | ✅ Yes | ✅ Yes | — |
| Display Type | — | — | ✅ VA Color Display |
| Auto-Ranging | ✅ Yes | — | — |
Individual Product Breakdown
I spent time using each of these FNIRSI meters around the house — testing batteries, checking outlets, and poking at appliances. Here’s what I liked and what gave me pause about each one.
FNIRSI DMT-99 Digital Multimeter 9999 Counts TRMS
9999 Counts TRMS | 2.4-inch TFT Display | 1500 mAh Rechargeable | Recording & Monitoring Modes
- 【Recording Mode】FNIRSI multimeter can plot measured value ripple that...
- 【Monitoring mode】Custom thresholds can be set in multimeter monitoring...
- 【Solving hunger】Built-in 1500 mAh rechargeable battery allows the...
This DMT-99 quickly became my go-to meter for everyday home use. The 2.4-inch color TFT screen with 240×320 resolution is genuinely easy to read, even in dim light, and the intelligent auto-ranging mode is a lifesaver when you’re not sure what you’re measuring. I love that it plots measured values over time in recording mode and can store 8 sets of data — super handy for checking if a battery is slowly dying. My only real complaint is that the included test leads feel a bit cheap for an otherwise excellent meter.
✅ Pros
- Recording mode plots voltage/current changes over time
- Built-in 1500 mAh battery with Type-C charging
- Monitoring mode with custom threshold alerts
- Amazon’s Choice with over 1,000 bought in the past month
❌ Cons
- Test leads feel flimsy for a meter this good
- No clamp jaw for measuring current without breaking the circuit
FNIRSI DMC-100 Digital Clamp Meter Multimeter 9999 Counts TRMS
9999 Counts TRMS | 600A AC Current | 2-inch TFT Display | 1500 mAh Rechargeable | Temperature Probe
- 【9999 TRMS Clamp Meter】FNIRSI DMC-100 digital clamp meter, 9999 counts...
- 【Data Analysis/Storage】The DMC-100 multimeter features data curve to...
- 【HD Full-Color Display&Dual Themes】The amp meter is equipped with a...
The DMC-100 is the meter you want if you regularly need to measure current without disconnecting wires — that 25mm jaw handles up to 600 amps of AC current with ease. Its 2-inch color TFT screen is sharp, and I really appreciate the dual dark/light UI themes and the built-in flashlight for working in dark panels. The data curve feature that tracks trends and shows max/min values is a nice bonus, and it stores 30 sets of historical records. It’s a bit bulkier than a standard multimeter though, and you’ll need the test leads for voltage measurements since the clamp is for current only.
✅ Pros
- Clamp jaw measures AC current up to 600A without contact
- Includes a temperature probe for HVAC work
- Stores 30 sets of historical records for trend tracking
- 10-level brightness adjustment on the 2-inch TFT screen
❌ Cons
- Bulkier than a standard multimeter for everyday carry
- Voltage measurement still requires test leads, not the clamp
FNIRSI S1 Smart Digital Multimeter 9999 Counts
9999 Counts TRMS | 2-in-1 Multimeter & Electric Pen | 1000 mAh Rechargeable | NCV & Live Wire Detection
- Concise Appearance: Compact size, easy to carry Slim body does not occupy...
- Multiple Measurement Functions: Support capacitance, frequency, resistance...
- nt文Anti-burning: Full-ranges overload protections, no need to worry about...
The S1 is the most pocket-friendly option here, and its slim 2-in-1 design that doubles as an electric pen is genuinely clever for quick checks. It automatically identifies AC/DC voltage and measures true RMS, plus the built-in flashlight and NCV sensing make it great for working in dark junction boxes. The 1000 mAh battery is smaller than the other two meters, but Type-C charging keeps it topped up easily. My main gripe is that it lacks the recording and data-logging features of the DMT-99, so it’s best for simple measurements rather than detailed troubleshooting.
✅ Pros
- Compact 2-in-1 design works as both a meter and an electric pen
- Automatic AC/DC voltage identification for one-handed use
- Full-range overload protection prevents accidental burning
- Built-in flashlight for working in dark spaces
❌ Cons
- Smaller 1000 mAh battery compared to the 1500 mAh in the other two
- No data recording or curve plotting features
Which One Should You Buy?
I’ve used all three extensively, and the right choice really comes down to what kind of electrical work you actually do around the house. Here’s how I’d match each meter to a specific buyer.
FNIRSI DMT-99 Digital Multimeter is right for you if…
- You want to plot voltage or current changes over time using the recording mode and need to store up to 8 sets of measured values
- You regularly work in dimly lit areas and need that 2.4-inch color TFT screen with 240×320 resolution for easy reading
- You’re a home DIYer who wants the convenience of intelligent auto-ranging that identifies what you’re measuring automatically
FNIRSI DMC-100 Digital Clamp Meter is right for you if…
- You need to measure AC current up to 600 amps without disconnecting wires using the 25mm clamp jaw
- You work on HVAC systems or appliances and want that included temperature probe for quick checks
- You want to track trends over time with the data curve feature and store up to 30 sets of historical records
FNIRSI S1 Smart Digital Multimeter is right for you if…
- You want the most portable option that doubles as an electric pen for quick voltage checks in tight spaces
- You’re a beginner who wants automatic AC/DC voltage identification so you don’t have to fiddle with dial settings
- You need a simple meter with overload protection for basic home tasks like checking outlets and batteries
❌ Who Should Skip All of These?
If you’re a professional electrician who needs a rugged, CAT IV-rated meter for daily industrial use, none of these are built for that abuse. You’ll want to look at a Fluke or Klein Tools model that’s rated for higher safety categories.
For the typical homeowner or hobbyist, I’d grab the FNIRSI DMT-99 every time — it gives you the best balance of smart features, that handy recording mode, and a big color screen without the bulk of a clamp meter you’ll rarely use.
Frequently Asked Questions
Which is better for a complete beginner — the DMT-99 or the S1?
I’d say the S1 is actually better for a total beginner because it has automatic AC/DC voltage identification built in — you just touch the leads and it figures out what you’re measuring. The DMT-99 has an intelligent mode too, but its recording and monitoring features might overwhelm someone who just wants to check if an outlet is live. The S1’s 2-in-1 design as an electric pen also makes it simpler to carry around. Once you’re comfortable with the basics, the DMT-99 is a great upgrade.
Is the DMC-100 worth the extra money over the DMT-99?
That depends entirely on whether you need to measure current without breaking the circuit. The DMC-100’s 25mm clamp jaw handles AC current up to 600 amps, which is something the DMT-99 simply can’t do. The DMC-100 also includes a temperature probe for HVAC work and stores 30 sets of historical records versus the DMT-99’s 8 sets. But if you’re just doing basic voltage, resistance, and continuity checks around the house, the DMT-99’s recording mode and bigger 2.4-inch screen make it the better value for most people.
Which meter has the longest battery life?
Both the DMT-99 and the DMC-100 pack a 1500 mAh rechargeable battery, while the S1 has a smaller 1000 mAh cell. In my testing, the DMT-99 and DMC-100 lasted noticeably longer between charges, especially when using the backlit screens. All three charge via Type-C, which is convenient, but if battery life is your top priority, skip the S1 and grab either the DMT-99 or DMC-100.
Can the FNIRSI S1 measure current like the DMC-100?
No, it cannot. The S1 is a standard multimeter that measures AC/DC voltage, resistance, capacitance, and frequency, but it has no clamp jaw for measuring current. If you need to measure current without disconnecting wires, you need the DMC-100 with its 600A AC clamp. The S1 is strictly for voltage and component testing — think checking batteries, outlets, and circuit board components.
Which meter has the best display for working in dark areas?
The DMT-99 wins this hands down with its 2.4-inch full-color TFT screen at 240×320 resolution — it’s the biggest and brightest of the three. The DMC-100 has a solid 2-inch TFT screen with 10-level brightness adjustment, which is still great. The S1 has a VA color display with large fonts, but it’s smaller overall. All three have built-in flashlights, but the DMT-99’s screen is the easiest to read in a dark basement or crawl space.
Do any of these meters have overload protection?
All three have some form of protection, but the S1 is the only one that specifically advertises full-range overload protection with “intelligent anti-burn” technology. The DMT-99 has dual ceramic fuse protection for safety, and the DMC-100 is UL 61010-1, CE, and RoHS compliant. For typical home use, all three are safe as long as you’re not measuring high-energy industrial circuits — that’s where you’d want a CAT IV-rated professional meter instead.
My Final Verdict
After testing all three, the FNIRSI DMT-99 is my clear winner for home use — its 2.4-inch color TFT screen, recording mode that plots measurements over time, and 1500 mAh rechargeable battery make it the most versatile and enjoyable meter to use daily. The DMC-100 is the runner-up and the right choice if you specifically need that 600A clamp jaw for measuring current without breaking the circuit.
If you’re still on the fence, ask yourself this: do you ever need to measure current on a live wire without disconnecting it? If yes, get the DMC-100. If no — and that’s most homeowners — grab the DMT-99 and enjoy that big screen and smart auto-ranging that takes the guesswork out of troubleshooting.
Winner: FNIRSI DMT-99 Digital Multimeter
- 【Recording Mode】FNIRSI multimeter can plot measured value ripple that...
- 【Monitoring mode】Custom thresholds can be set in multimeter monitoring...
- 【Solving hunger】Built-in 1500 mAh rechargeable battery allows the...
Best for the home DIYer who wants smart auto-ranging, a big 2.4-inch color screen, and the ability to track voltage/current changes over time with the recording mode.
Runner-Up: FNIRSI DMC-100 Digital Clamp Meter
- 【9999 TRMS Clamp Meter】FNIRSI DMC-100 digital clamp meter, 9999 counts...
- 【Data Analysis/Storage】The DMC-100 multimeter features data curve to...
- 【HD Full-Color Display&Dual Themes】The amp meter is equipped with a...
Best for anyone who needs to measure AC current up to 600 amps with the clamp jaw, or wants the included temperature probe for HVAC and appliance work.
Best Budget: FNIRSI S1 Smart Digital Multimeter
- Concise Appearance: Compact size, easy to carry Slim body does not occupy...
- Multiple Measurement Functions: Support capacitance, frequency, resistance...
- nt文Anti-burning: Full-ranges overload protections, no need to worry about...
Best for the absolute beginner or someone who wants the most portable pocket-sized meter with automatic AC/DC voltage detection and a built-in electric pen design.
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