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Small, fast calculators for insulation resistance, PI and DAR, motors, cables and power. Open one, type your readings, get a verdict.
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From what a megger measures to reading PI and DAR like a pro.
- 1 Insulation Resistance Testing: What It Is and How to Do It Insulation resistance testing is the single most important test you can run on any electrical installation. Learn the test voltages, procedures, and how to read the results. 9 min read
- 2 What Is a Megger? How to Use a Megohmmeter for Insulation Testing A megger tests the one thing a regular multimeter can't - whether your cable or motor insulation will survive operating voltage without breaking down. 9 min read
- 3 Insulation Resistance Temperature Correction Explained A megger reading of 80 MΩ one day and 30 MΩ the next isn't necessarily a winding going bad - it might just be a colder motor versus a hot one. 5 min read
- 4 Polarization Index vs Dielectric Absorption Ratio Two time-based insulation tests compared, with typical interpretation guides. 6 min read
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Instruments
Insulation testersWhy earthing matters, how low is low enough, and how to test soil.
- 1 What Is Electrical Earthing? Types, Methods, and Why It's Non-Negotiable Earthing is not optional - it is the last line of defence between a fault and a fatal shock. Here's how every earthing system works and why testing it matters. 8 min read
- 2 Earth Resistance Testing: Why It Matters and How to Measure It A poor earth connection is the most invisible and most dangerous electrical fault. This guide explains earth resistance, accepted limits, and how to measure it correctly. 8 min read
- 3 How Low Should Earth Resistance Be? There is no single number. Here is where the targets come from and what to do when you miss one. 6 min read
- 4 Soil Resistivity Testing: Wenner vs Schlumberger Two four-pin methods compared, and how to read the resistivity curve for earthing design. 6 min read
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Instruments
Earth testersMultimeter or clamp? True RMS or not? Decide with confidence.
- 1 What Is a Multimeter? A Complete Guide to How It Works A multimeter is the most essential instrument in any electrician's or engineer's toolkit. This guide breaks down exactly how it works - from basic physics to practical usage. 8 min read
- 2 How to Choose a Multimeter: Complete Buying Guide for 2026 There are hundreds of multimeters on the market. This guide cuts through the noise - CAT ratings, True RMS, resolution, and what actually matters for your type of work. 8 min read
- 3 Clamp Meter vs Multimeter: Which Tester Do You Actually Need? Both measure electrical quantities - but they work very differently. Here's a practical breakdown of when to reach for a clamp meter versus a multimeter. 7 min read
- 4 True RMS vs Average RMS: Why It Matters for Your Multimeter Most cheap multimeters assume a perfect sine wave. Modern loads - VFDs, inverters, switch-mode supplies - are not sine waves. Here's why True RMS matters. 6 min read
Calculators for this
Instruments
MultimetersControls, waveforms, bandwidth and what to buy.
- 1 How to Use an Oscilloscope: A Complete Beginner's Guide An oscilloscope turns invisible electrical signals into visible waveforms you can measure. This complete guide takes you from unpacking to your first real measurement. 10 min read
- 2 How to Read an Oscilloscope Waveform: Voltage, Time, Frequency The oscilloscope screen is a graph - once you know what the axes mean and what each waveform type looks like, every signal tells a story. Here's how to read it. 9 min read
- 3 Oscilloscope Bandwidth Explained: Why It Matters Bandwidth isn't just about sine waves - it determines how sharp an edge your scope can show at all, and no amount of sample rate can make up for a shortfall. 6 min read
- 4 How to Choose an Oscilloscope: A Buying Guide Bandwidth, sample rate, channels, and memory depth all trade off against each other. Here's how to size an oscilloscope to the signals you actually need to see. 8 min read
Calculators for this
Instruments
Vartech oscilloscopesLibrary
Browse by topic
10 guides
Physics and fundamentals
Ohm’s law, AC/DC, ratings and specs.
9 guidesMultimeters
Choosing and using the essential tool.
8 guidesClamp meters
Current without breaking the circuit.
27 guidesInsulation and earthing
Meggers, earth testers, motor tests.
15 guidesScopes and signals
Waveforms, generators, LCR meters.
9 guidesPower supplies and loads
Linear, SMPS and programmable.
7 guidesCalibration
4-20 mA loops and intervals.
12 guidesEnvironmental
Light, sound, airflow, temperature.
8 guidesPower quality
Phase sequence, harmonics, PF.
11 guidesRelay and HV testing
Protection relays, dielectric tests.
5 guidesBench and repair
Soldering, fuses, batteries.
Latest
Fresh from the blog
Guide
Measuring DC Current with a Clamp Meter
An AC clamp reads zero on DC. Here is how DC clamps work and how to use one.
17 Oct 2026 · 7 min read
ExplainerGhost Voltage, Low-Z Mode and NCV Explained
A dead cable reading 90 V is usually ghost voltage. Here is how to tell.
17 Oct 2026 · 6 min read
ComparisonDCM 2250 TR vs DCM 5410 TR: Which Clamp Meter?
One spec line separates these two clamps: DC current. Which do you need?
17 Oct 2026 · 5 min read
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