The capacitance symbol on a digital multimeter (DMM) dial is most commonly represented by a parallel T-bar icon (⊣⊢), the letter "F" (for Farads), or the abbreviation "CAP". On electrical schematics, the symbol appears as two parallel lines, though the exact geometry changes depending on whether the drawing follows North American (ANSI) or International (IEC) standards. If your meter reads out of limits or the component markings are rubbed off, knowing how to interpret these symbols and safely test the component is the difference between a successful repair and a blown meter fuse.
Multimeter Dial & Schematic Symbol Reference Table
Before you touch your probes to a capacitor, verify you are looking at the correct symbol. The table below maps the exact markings you will find on modern DMMs (like the Fluke 87V or Brymen BM235) and the corresponding schematic symbols used in circuit diagrams.
| Context | Symbol / Marking | Standard / Region | Practical Meaning & Application |
|---|---|---|---|
| DMM Dial (Icon) | ⊣⊢ (Parallel T-bars) | Universal | Dedicated capacitance test mode. Applies an AC test signal to measure charge time. |
| DMM Dial (Text) | CAP or F | Universal | Abbreviation for Capacitance or Farads. Often shares a dial position with the Ohms (Ω) setting. |
| Schematic (Non-polarized) | || (Two straight lines) | IEC 60617 / ANSI 315 | Ceramic, film, or mica capacitors. Can be installed in either direction. |
| Schematic (Polarized) | |+ (One curved line) | ANSI/IEEE 315 (US) | Electrolytic or tantalum capacitors. The curved plate represents the negative (outer foil) terminal. |
| Schematic (Polarized) | ||+ (Two straight lines + plus) | IEC 60617 (EU/Global) | Electrolytic or tantalum capacitors. Both plates are straight; polarity is indicated strictly by the '+' sign. |
| Component Body | EIA 3-Digit Code (e.g., 104) | Global (Ceramics) | First two digits are significant figures, third is multiplier in picofarads (104 = 100,000 pF = 100 nF). |
Rows People Get Wrong (And How to Fix Them)
Even experienced hobbyists make assumptions based on these symbols that lead to inaccurate readings or damaged boards. Here is where the confusion happens and how to correct it.
Mistake 1: Confusing the Dial Icon with Continuity
The capacitance icon (⊣⊢) looks vaguely similar to the continuity or diode test symbols on some cheaper multimeters. If you attempt to measure a capacitor using the continuity setting, the meter will simply beep if the capacitor is completely shorted, or do nothing if it is open. It will not tell you if a 100µF capacitor has degraded to 12µF. Always ensure the dial is physically clicked into the CAP or ⊣⊢ detent, and allow the meter to auto-zero its internal test leads before connecting the component.
Mistake 2: Misreading Polarized Schematic Standards
If you are repairing a device designed in the US, the schematic will likely use the ANSI standard (one straight plate, one curved plate). The curved plate is always the negative terminal. However, if you are working from a European or Asian schematic using the IEC standard, both plates will be drawn straight, and polarity is indicated only by a small '+' sign next to the positive terminal. Assuming the curved plate rule applies globally will cause you to install electrolytic capacitors backward, leading to catastrophic venting or explosion under load.
Mistake 3: Measuring In-Circuit
A multimeter measures capacitance by outputting a small known current and measuring the voltage ramp-up time. If you measure a capacitor while it is still soldered into the board, parallel impedances (resistors, IC pins, other capacitors) will skew the charge curve. The meter might display a wildly inflated value or throw an 'OL' (Over Limit) error. You must desolder at least one leg of the capacitor to isolate it from the circuit before taking a capacitance reading.
Faded Markings & Safe Interpretation of Unknown Capacitors
Capacitors in older power supplies or CRT monitors often suffer from heat damage, causing the silk-screened text and values to fade completely. When you cannot read the component body, your multimeter is your only reference—but you must follow a strict safety protocol first.
Never connect a multimeter's capacitance probes to a capacitor that has not been explicitly discharged. A charged capacitor will feed voltage back into the meter's sensitive capacitance measurement circuitry, instantly blowing the internal protection fuse or destroying the ADC chip. Furthermore, never discharge a high-voltage capacitor by shorting it with a flathead screwdriver. The instantaneous current spike can spall the internal dielectric, weld the screwdriver to the terminals, and shower you with molten metal.
The correct method: Build a discharge tool using a 20kΩ, 5-watt wirewound resistor attached to insulated alligator clips. Clamp the resistor across the capacitor terminals for 5 to 10 seconds, then verify the voltage is below 1V using your multimeter's DC voltage mode before switching to the capacitance (⊣⊢) mode.
Decoding the EIA 3-Digit System
If the capacitor is a ceramic disc and the markings are partially visible, you will likely see a 3-digit code. This is not a direct value; it is a multiplier system based on picofarads (pF).
- Example: A marking of
104. - Math: The first two digits (10) are the base number. The third digit (4) is the number of zeros to add.
- Result: 10 followed by four zeros = 100,000 pF.
- Conversion: 100,000 pF = 100 nF = 0.1 µF.
If your multimeter reads 0.098 µF on the CAP setting, it confirms the component is a 104 ceramic capacitor operating within normal tolerance.
Frequently Asked Questions
Why does my multimeter display 'OL' when measuring capacitance?
'OL' stands for Over Limit (or Open Loop). On the capacitance setting, this usually means one of three things: the capacitor's value exceeds the maximum range of your specific meter (e.g., trying to measure a 10,000µF supercapacitor on a meter that maxes out at 100µF), the capacitor is completely open internally (a failed, dried-out electrolytic), or the capacitor still holds a residual charge that is blinding the meter's test circuit. Discharge the cap, verify your range, and test again. If it still reads 'OL' out-of-circuit, the component is dead.
Can I test a capacitor if my multimeter lacks a capacitance symbol?
Yes, but only qualitatively. If your meter only has an Ohms (Ω) setting, you can set it to a high resistance range (e.g., 2MΩ) and touch the probes to the capacitor. You should see the resistance value start near zero and slowly climb until it hits 'OL' as the capacitor charges from the meter's internal battery. If it stays at zero ohms, the capacitor is shorted. If it immediately reads 'OL' without climbing, it is open or too small to measure this way. This method proves the capacitor isn't dead, but it cannot tell you if a 470µF capacitor has degraded to 50µF. For quantitative diagnostics, a dedicated capacitance meter or an ESR meter is required.
What is the difference between the capacitance symbol and the diode test symbol?
They serve entirely different functions and use different internal meter circuits. The capacitance symbol (⊣⊢ or CAP) measures a component's ability to store an electrical charge by timing an AC voltage ramp. The diode test symbol (an arrow pointing at a line: ⊳|) measures the forward voltage drop of a semiconductor junction by pushing a small constant DC current (usually 1mA) through the component. Using the diode test mode on a capacitor will just show an 'OL' or a brief voltage spike as the cap charges, yielding no useful diagnostic data.
