We can use a Wheatstone bridge voltage measurement to determine an unknown resistance value. In part 3 of this series, we used Kirchhoff’s voltage law to derive the branch currents and node voltages for an unbalanced Wheatstone bridge with five known, fixed resistors (Figure 1). Now, we propose to replace R5 with a digital multimeter […]
Meters & Testers
Making sense of test circuits with Kirchhoff’s laws: part 3
Kirchhoff’s voltage law gives us three equations with three unknowns to solve for loop currents in an unbalanced Wheatstone bridge.
Making sense of test circuits with Kirchhoff’s laws: part 2
In part 1 of this series, we looked at ways to simplify resistor networks by identifying series and parallel combinations of resistors. We closed with a look at a version of the Wheatstone bridge, such as the one in Figure 1. Although it has only five resistors, not one of them is in series or […]
Tryout: two low-cost USB inline meters and a load
Despite their limited use for testing wall chargers and power banks, USB inline testers let you compare power sources. In three videos, we take you through their features, and we also try an inline USB electronic load. When testing a USB charger or power bank, you can connect a phone or other device and see […]
R&S digital multimeters feature 5.5 and 6.5 digits with triple displays
The UDS series from Rohde & Schwarz provides the company with a significant upgrade and place it against top competitors. Digital multimeters (DMMs) are a measurement staple, sitting alongside oscilloscopes, power supplies, and waveform generators on just about every engineer’s bench. You may not think of Rohde & Schwarz as a major competitor in the […]
Understanding ADC specs and architectures: part 5
ENOB describes an analog-to-digital converter’s performance with respect to total noise and distortion. In the earlier parts of this series on analog-to-digital converters (ADCs), we looked at the basics (part 1); gain error, offset error, and differential nonlinearity (part 2); and integral nonlinearity (part 3); and then we looked at some ADC topologies and introduced […]
Swapfest May 2025: test equipment
The May 2025 gathering of the monthly electronics “Flea at MIT” swapfest featured an excessive number of test instruments. We break them down into oscilloscopes, meters, and signal sources. Click on any image to enlarge in a new tab. Oscilloscopes A Tektronix analog modular oscilloscope. The black bezel hides the model number. This unit has […]
Teardown: HP 8112A pulse generator
This 50 MHz pulse generator was built as solid as a rock. It’s almost all metal. We take the unit completely apart and look at it from a system and board level. On a visit to the MIT swapfest in 2024, I came across an HP 8112A 50 MHz pulse generator. For $20, I brought […]
Modular system combines DMM with DAQ
The DAQ3120 from B+K Precision lets you install up to three measurement modules to create a custom system for your bench. Most engineers have a digital multimeter (DMM) for basic measurements such as voltage, current, and resistance. Sometimes, however, you need the flexibility to add channels and log measurements without or without a computer. That’s […]
APEC 2025 test equipment: oscilloscopes and probes
Oscilloscopes and probes play a vital role for engineers designing and testing power electronics. Delivering electrical power to analog and digital circuits and systems is more than just DC measurements. That’s because nearly all power-converter circuits use switching techniques to maximize efficiency. Silicon carbide (SiC and gallium nitride (GaN) transistors, with their higher voltage and […]
