Back to Basics: CAT Rating

Posted under Back to Basics, Educational on May 25th, 2025 by

Was in a bit of debate with a client last week about how CAT ratings apply to their multimeters. Thought I would clarify this topic properly.

CAT Rating

CAT (Category) rating is your first line of defence against voltage spikes. It’s a standardized safety label defined by IEC 61010-1 that tells you how much transient overvoltage protection your multimeter offers in various measurement environments. Transients are those short, high-energy spikes from switching operations, capacitor discharges or lightning strikes that can damage equipment or injure you. A meter’s CAT rating ensures its internal circuitry, insulation, spacing, and spark gaps can withstand these spikes without failure. Lower-rated instruments can blow internal fuses or even explode when used incorrectly.

CAT Rating

There are four CAT levels: CAT I to CAT IV. CAT I is for low-energy circuits not tied to mains, like battery-powered electronics or board-level testing. CAT II covers local mains-connected loads, such as household appliances and portable tools. CAT III suits building installations, distribution panels, switchgear, fixed motor controllers. CAT IV is reserved for the 3-Phase Utility Connections, outdoor lines, and high energy devices.

During certification, meters are subjected to impulse/surge tests at specified voltages with defined source impedances to simulate fault conditions. For example, CAT III at 600 V is tested at 6000 V impulse with a 2Ω source impedance, while CAT II at 1000 V uses a 6000 V impulse with 12Ω. This is where folks screwup. A higher working voltage rating does not necessarily mean greater safety. CAT III 600V meter (with higher transient withstand capability) offers more protection than a CAT II 1000V meter, although the later one has higher working voltage. Check the table. BTW, surge tests are not the same as ESD tests that you do. Surge tests have a longer and higher energy levels compared to ESD tests by more than an order of magnitude.

So remember about the CAT ratings next time you use multimeters. Also, don’t forget your test leads: they must carry the same CAT rating and voltage, else its useless.

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Advanced Tech: AiC and AiP

Posted under Back to Basics, Educational, Technology on May 18th, 2025 by

Antennas have been the driving force of the modern wireless industry for a long time, especially the antennas on PCBs. Microstrip patches, slot antennas, and F-antennas printed on substrates like FR4 give us reliable performance below 30 GHz. They let us tune frequency by adjusting patch dimensions and feed geometry. When we push into bands above 30 GHz, losses from copper roughness, substrate modes, and dielectric loss make PCB antennas inefficient and bulky.

To overcome the limits of PCB antennas, we are moving into two new approaches: Antenna-in-Package (AiP) and Antenna-in-Chip (AiC). In AiP, think of the antenna as part of the chip’s casing. It’s a miniature multi-layer printed-circuit board that just happens to have a bare RF chip solder-bumped into its centre and then gets shipped as a single surface-mount part. By printing or mounting the radiator onto the package substrate using low-loss organic laminates or ceramics, we ensure the materials do not absorb the signal. This lets us build small beam forming arrays and pack amplifiers, filters, and phase shifters right into the module.

AiC takes the idea all the way onto the silicon die. Here, we etch antenna shapes into the top metal layer of a CMOS chip. I’ve seen designers thicken that metal, add patterned ground shields beneath it, or insert artificial magnetic conductors to bounce more energy out of the lossy silicon. Some even place a thin cover (a superstrate) above the chip to help steer or focus the beam. Since silicon has a high permittivity and loses energy, it can’t get more efficient than a certain point.

AiC is an ultimate miniaturisation play, and AiP is the performance play. If you’re designing a smartphone or radar sensor today, AiP is the practical path, it gives you gain, beam-forming head-room and a cleaner PCB layout. You only pick AiC when absolute footprint has to be the size of the silicon itself, and you are pushing beyond 100GHz where antenna is only a few hundred microns long and PCB interconnects become impractical. To date, only a handful of functional antenna-on-chip prototypes have been demonstrated.

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