https://community.element14.com/technologies/test-and-measurement/The electronic test and measurement group is intended to prove information on electronic test and measurement equipment, including thermal imaging technology, and also answer any questions you may have.en-USTelligent Community 12https://community.element14.com/technologies/test-and-measurement/b/blog/posts/spice-circuit-simulation-a-simple-explanationTue, 14 Apr 2026 02:23:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:7328923d-6cc9-4c05-ad7a-2907e1d272d3shabazTable of Contents Introduction I Want to Try It, Now! SPICE Quick Overview Elementary Models Pin Ordering for Component Symbols An Entire Circuit Choosing and Running Simulations DC Voltages and Currents (Operating Point) Simulations Time-Domain (TRAN) Simulations Frequency Response Simulations (AC) Summary Further Information Introduction Circuit simulation is powerful, and can be very accurate, depending on the how closely the circuit has been modelled to the actual circuit. It can save a lot of time to simulate, before constructing for real. There are different kinds of circuit simulation engines, and different types of simulations to want to run, and some are more appropriate for particular niches in electronics engineering. The engine discussed in this blog post is called SPICE , and it is broadly used in electronics. SPICE dates back to the 1970’s, although the version used today was developed in the late 1980’s. Despite its ancientness, it is used professionally for simulating circuits containing passive components, discrete semiconductors as well as various integrated circuits, and the breadth of typical circuits can include (but is not limited to) amplifiers, filters, power supplies, oscillators and so on. SPICE is even used to an extent, to simulate custom integrated circuit designs (or at least subcircuits). This blog post explores some of the popular capabilities of SPICE, and how it can be employed with CAD schematic entry software. I use example screenshots from KiCad, but this blog post is not KiCad specific; the concepts described work with other software too, such as LTspice. I Want to Try It, Now! If you want to explore for yourself, it’s very easy, a five-step process. Here are the steps, using an example project by michaelkellett which is an audio preamplifier. Please note this won’t teach how to use KiCad (that requires some self-training, for instance using this 50-minute video: Creating Circuit Boards with KiCad ), nor will it cover all aspects of SPICE, but will show how to run a simulation and explain how SPICE works, so that the benefits of SPICE can be explored further by those interested. 1. Download and install KiCad 10 2. Download the discrete_amps project zip file and extract it to anywhere on your PC 3. Run KiCad, open the extracted preamp_k2 project, and open up the schematic 4. Click on Inspect->Simulator 5. You’ll see several simulation tabs. Click to select any of them, then click on the triangle RUN icon! SPICE Quick Overview There’s a simulation engine for electronics called SPICE, which traditionally ran on mainframes. It relies on internal models for various basic components such as resistors, capacitors and transistors, and accepts parameters as inputs to tweak the models for each component. Then, an entire circuit can be described as a collection of models and their wiring to each pin in the model. Finally, the desired type of simulation can be chosen, and SPICE will run it, and spit out a dataset, which can be charted. Desktop CAD software can incorporate the SPICE engine, but in the background, the transfer of information between the CAD software and the SPICE engine is based on text-based files. That’s because SPICE follows the traditional batch-processing paradigm that was popular with mainframes. A user would prepare a set of instructions, send them to the computer, and then come back later to see the generated results. Today, the user would sketch a circuit graphically, but in the background KiCad (or any other software that uses SPICE) will prepare text files describing the components and circuit, and call the SPICE engine passing the text file names on the command line, and in return, SPICE will generate a file of results. The CAD software will then chart the results graphically from the results file. As far as the user is concerned, they need never know that text data was exchanged to make the simulation occur. Elementary Models As mentioned, SPICE’s internal models (such as an NPN transistor model) rely on parameters to tweak the model to represent specific components, such as a BC549 NPN transistor. For instance, for an NPN or PNP transistor, one of the parameters would be the voltage across the base-to-emitter when current is flowing into the base. The transistor datasheet would be consulted to determine that voltage (it may be say 0.7V) and then the model would be configured by the following parameter setting: VJE = 0.7 This would take ages since there can be a lot of parameters for a component model, so instead, one would download the manufacturer-supplied model file, which can have various suffixes, but .lib is common. A BC549 transistor would have a SPICE model file called BC549.lib and it would contain a list of the parameters, all ready for simulating that transistor. In the example snippet below, the top part contains comment lines, followed by the model name BC549/550 and the NPN model type instruction to SPICE that indicates which model type to apply (for instance, for say N-channel mosfets, the model type field would need to be set to NMOS ). After that, all the parameter settings for that model type follow. * BC549/550 NPN EPITAXIAL SILICON TRANSISTOR ELECTRICAL PARAMETERS *-------------------------------------------------------------------- * Switching and Amplifier * Vcbo & Vceo: BC549(Vcbo:30V / Vceo:30V) * BC550(Vcbo:50V / Vceo:45V) *-------------------------------------------------------------------- * MODEL PARAMETERS FROM MEASURED DATA: BC549 *-------------------------------------------------------------------- .MODEL BC549/550 NPN + LEVEL = 1 + IS = 2.24183E-14 + NF = 0.996496 + ISE = 1.90217E-14 + NE = 2 + BF = 228.4 The above is known as an elementary model. Pin Ordering for Component Symbols The model described above needs to somehow be mapped onto a graphical symbol, and some way of assigning pins is required. For instance, the NPN circuit symbol may have pins called B, C, E, or one may choose to call the pins BASE, COLLECTOR, EMITTER. SPICE works with any desired pin naming, it just use the order to determine which is which; internal to SPICE, each elementary model has a specific hard-coded pin order, and for NPN transistors the order happens to be collector, base, emitter. You wouldn’t know that order without delving into SPICE documentation, but ordinarily one doesn’t need to know this to use SPICE. The model so far only tells SPICE how to model the transistor, but it doesn’t tell SPICE what pins go where. That needs to be further input into SPICE, and that input can be self-generated by KiCad or whatever desktop software the user is using with SPICE. So, when a NPN symbol is created and drawn up in a symbol editor tool, there will be a drop-down menu that will either allow the user to assign each pin name to a order (i.e. if you name the collector pin “C”, then you would need to assign “C” to “1” since SPICE expects the collector pin to be listed first), or the symbol editor tool will have been pre-programmed with the expected order for each model type, and will allow the user to assign the “C” pin to “Collector” in the drop-down menu. The screenshot below shows a user assigning a pin called “E” to the BC549 model. An Entire Circuit Whenever a circuit contains a BC549 transistor, KiCad will automatically provide SPICE with an explanation of that, with a line such as: Q1 Net-_Q1-C_ Net-_Q1-B_ Net-_Q1-E_ BC549/550 The above line indicates that the user’s circuit contains a BC549 transistor that the user has labeled as Q1 . The fields beginning with Net- just happen to be names that KiCad decided to give to each wire drawn in the circuit, and the wire name connected to the BC549 collector has to be listed first, because the SPICE internal NPN model requires that to come first as mentioned earlier. Sometimes a user will create their own signal (i.e. net) names in the schematic, for instance the wire connected to the BC549 base may be named INPUT , and in that case, KiCad will choose to use the user-provided net name: Q1 Net-_Q1-C_ /INPUT Net-_Q1-E_ BC549/550 In summary, KiCad will provide SPICE with a list of all the components and their connections, and the model names, as shown in the example line above. It’s sometimes called a netlist . The netlist snippet below would correspond to a circuit containing a capacitor, two transistors, and a resistor. C1 Net-_Q1-E_ Net-_C1-Pad2_ 22u Q1 /BOB Net-_Q1-B_ Net-_Q1-E_ BC549/550 Q2 Net-_Q2-C_ /INPUT Net-_Q2-E_ BC549/550 R5 Net-_Q1-E_ Net-_Q3-E_ 16k Choosing and Running Simulations Now that SPICE is aware of component models, and the circuit topology, it can be made to run a desired simulation (technically known as an analysis ). SPICE offers different analyses, of which the following three are typically encountered (others are too, but I will only cover these three for now, and may add more to this section later). DC Voltages and Currents (Operating Point) Simulations When designing a circuit, often the user needs to bias components to operate in a certain region, and then perhaps a varying signal is applied. This is easiest to picture with an amplifier circuit. The transistors would been to be placed into a region where they are passing some current, so that later when a varying audio signal arrives, that signal will linearly affect the amplified output. A DC Operating Point simulation tries to calculate such initial voltages and currents in the circuit when no varying signals are present. It’s as if a user applied a multimeter to locations in a circuit. When KiCad (or any other software application that uses the SPICE engine) runs such a simulation, the output will be a list of these voltages and currents for each wire in the circuit. Here is a snippet of example output: I(q1:c): 101.647uA I(q1:b): 432.641nA I(q1:e): -102.079uA V(net-_q1-b_): 1.31966V V(/in): 0V P(c2): 0.00114469fW V(net-_c3-pad1_): 5.63932V P(c3): -3.82135e-05fW Most users won’t ever need to follow that, and will instead look to see how the desktop software displays it graphically; in the screenshot below, it can be seen that the voltage at Q1 base is 1.32V, and the current flowing through the collector is 102 uA. Both of those values are also in the text output above. Time-Domain (TRAN) Simulations What SPICE calls a TRAN (short for Transient) analysis is really an oscilloscope-like simulation of all the voltages and currents in a circuit, as if an oscilloscope voltage or current probe were applied everywhere. Imagine testing a real circuit, where first a user may use a multimeter, which is close to what a DC Operating Point analysis (as discussed earlier) achieves, and then the user connects up the oscilloscope, which is what a TRAN analysis is closest to. Much like how an oscilloscope is set to a certain timebase (time per division) setting and then the oscilloscope Run/Stop button is pressed to capture the signal values over a period of time, the TRAN analysis is configured near-identically. Usually you need to choose the start and stop time and the step time for each sample of results. As with any other analysis, SPICE will output a load of values, but KiCad will also display them graphically. A user can choose which signals are of interest, and those will be displayed just like if an oscilloscope was being used. In the example in the screenshot below, the user has selected to view one signal, but others could be chosen too, just like oscilloscope channels. An important thing to note, is that unlike an oscilloscope, SPICE does not run continually. It’s a one-time simulation. If changes are made to the circuit, then the simulation needs to be rerun. In contrast, with an oscilloscope, you can make changes to a circuit and watch the effects in real-time. A few rare software tools can provide simulations that look real-time, but in the background, they are likely repeatedly running the SPICE engine for small periods of time, and updating the chart each time, thus making it appear dynamically updated. It can work really well, but unfortunately KiCad doesn't support that (and neither does LTspice , TINA/Spice , PSPICE , and so on). Frequency Response Simulations (AC) SPICE has an analysis called AC , which applies a swept frequency stimulus signal, and records the output at each frequency. CAD software can read the output file, and convert to gain and phase values and plotted as would a frequency response analyzer test tool. This sort of simulation is highly useful for examining filter bandwidths, and seeing if an audio amplifier has a flat response or not, for example. SPICE needs to be told what frequency range to use; for an audio amplifier, one might select from 10 Hz to 100 kHz perhaps. The screenshot below shows that the user was interested to see the simulation run up to 10 MHz (which is typed as either 10Meg , or 10e6 , and _not_ 10M; this is an artifact from SPICE’s heritage). Unlike the earlier analyses (DC Operating Point and Transient), to be useful, the AC analysis always requires the SPICE engine to be instructed where the stimulus signal is to be applied. With KiCad, a sine-wave stimulus is indicated directly on the schematic, by placing a component called VSIN from KiCad’s supplied Simulation_SPICE library and wiring it to the circuit just like any other component. The stimulus source needs some configuration to work with SPICE. In KiCad, this is entered by double-clicking on the symbol and editing a symbol property: Technically all that is required is for that line to always state AC 1 (this scales the values to read correctly) however it’s useful to precede it with something like SIN(0 1m 1k) because that is then useful for TRAN simulations which may benefit from sine wave stimulus too (it depends on the circuit in question). The values 0, 1m and 1k represent the DC offset, Vpeak amplitude, and frequency, i.e. a sine wave with 1 mV peak (2 mV p-p) and 1 kHz frequency. Since the ordering may be hard to remember, it’s possible to place comments after a semicolon: The screenshot below shows what the simulation results can look like. SPICE will have generated a file containing detail for each connection in the circuit, across the specified range of frequencies. The user can select the signals of interest, and the software will chart the frequency response. Summary SPICE allows the user to perform analyses (i.e. simulations) to achieve measurements of the type that could be performed in real life with a multimeter, oscilloscope and frequency response analyzer. Other types of simulation are possible too. SPICE is text-file based, and manufacturers supply model files containing parameters or netlists for more complex devices and subcircuits, which can be assembled into a circuit netlist by CAD software such as KiCad, based on a schematic a user may create. When instructed to run a simulation based on those text files, SPICE will generate output in text form, which the CAD software can present graphically. Thanks for reading! Further Information (+) KiCad 8: Working with Circuit Simulations! - element14 Community (+) KiCad 10 and SPICE: Practical Tips for Working with Circuit Simulations! - element14 Community SPICE3 User Manual (PDF) Preamp circuit discussion (see the comments sections below the blog)kicadsimulationcircuit simulationcadspicehttps://community.element14.com/technologies/test-and-measurement/b/blog/posts/researchers-create-a-new-technique-that-produces-mxenes-with-160x-conductivityThu, 09 Apr 2026 19:32:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:9d7531ee-e528-4519-9b1b-d52fb53b9fa3CatwellThis image combines a scanning electron microscopy (left) and a crystallographic fragment of the MXene structure, highlighting its ordered and finely tuned surface terminations. (Image Credit: B. Schröder/HZDR) Researchers from Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and other institutions have developed a new method to produce MXenes with exceptional purity and control. This gas-liquid-solid (GLS) process enables the synthesis of pure MXenes with halogen atoms evenly distributed across the surface, allowing for precise adjustment of the surface composition. Overall, the method significantly enhances the electrical conductivity, paving the way toward high-performance sensors, electronics, and energy technologies. MXenes, identified in 2011, are an expanding class of inorganic 2D materials. These structures have layers---each one containing transition metals bonded with carbon or nitrogen. Meanwhile, the outer surfaces feature attached halogen atoms that influence the properties of the material. Usually, researchers rely on chemical etching to create MXenes, and these lead to a random distribution of surface terminations, like oxygen, fluorine, or chlorine. The new approach uses MAX phases (solid starting materials), molten salts, and iodine vapor to create MXene sheets. Working together, the molten salts and iodine vapor control the binding of halogen atoms, like iodine, bromine, or chlorine, to the surface. With this method, MXenes have extremely uniform, well-ordered surface terminations and significantly reduced impurities. The researchers used this method to synthesize MXenes from eight MAX phases (Ti3AlC2, Ti3AlCN, Ti2AlC, Ti2AlN, TiNbAlC, Nb2AlC, Nb4AlC3, and Mo2Ga2C), demonstrating its practicability. They also used density functional theory (DFT) calculations to examine how surface terminations affect MXenes’ stability and electrical properties. Highlighting the significance of this technique, the team investigated Ti3C2 (titanium carbide MXene). Standard synthesis methods (chemical routes) produce Ti3C2 with a combination of chlorine and oxygen terminations that degrade the electrical properties. On the other hand, using the GLS technique to produce Ti3C2Cl2 contains only chlorine---arranged in an ordered structure with no impurities. “The results were striking. The chlorine-terminated MXene variant showed a 160-fold increase in macroscopic conductivity and a 13-fold enhancement in terahertz conductivity compared with the same material made by traditional methods. In addition, a nearly fourfold increase in charge carrier mobility was observed, a key measure of how freely electrons move through a material,” Dr. Dongqi Li from TU Dresden said. Performance improvements like these occur due to the more controlled surface chemistry. Uniformly arranging the chlorine atoms on the MXene surface allows the electrons to flow more freely due to fewer obstructions in their path. The team ran quantum transport simulations to verify that the smooth surfaces lowered electron trapping and scattering, which explains performance enhancements. The team’s work demonstrates that controlling the surface halogen type affects the electromagnetic waves’ absorption characteristic of MXenes. Controlling the material like this enables it to be used in certain applications like electromagnetic shielding, radar-absorbing coatings, and next-gen wireless components. Chlorine-terminated MXenes demonstrate strong absorption in the 14-18 GHz frequency range. Bromine- and iodine-terminated MXenes have different frequency absorption ranges. Have a story tip? Message me here at element14.researchsignalon_campusconductivitysemiconductoruniversitypowerinnovationhttps://community.element14.com/technologies/test-and-measurement/b/blog/posts/shahe-wireless-bluetooth-digital-calipers-a-quick-reviewSat, 21 Mar 2026 13:15:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:40138fdd-e66e-4fd2-955a-62f39b007d43shabazIntroduction I own two pairs of high-quality Moore & Wright calipers, which offer several advantages: an excellent LCD screen, soft-press buttons, and straightforward operation. However, there are some drawbacks. The battery compartment slide cover can become loose and eventually be lost, and the battery itself is fiddly to remove. Over the years, I lost both the battery cover and the locking screw. Additionally, the battery runs out of juice and needs replacement every few months, which is inconvenient. I prefer left-handed digital calipers, which are quite rare for a high-quality product at a reasonable price - Moore & Wright, for example, does not offer them. I wondered if Bluetooth calipers might suit me better, as I could hold them in any orientation without worrying about seeing the on-device display. I considered purchasing Bluetooth calipers locally from the same organization (their parent company, to be exact) and was quoted £236, plus an additional £106 for a Bluetooth dongle for the PC if needed. I appreciate it's unfair to compare prices for locally supplied and supported products, but sadly, while these prices might be acceptable for some businesses, they were not viable for me. After all, calipers are typically stated accurate to +-0.02 mm - not at the level of an ultra-high-precision instrument such as a micrometer. As I am not a machinist or mechanical engineer, I cannot assess the demand for calibration certificates at this level of measurement. After some research, I discovered that Wenzhou Sanhe Measuring Instrument Co.’s website offered a range of calipers , with a specified accuracy of +-0.02 mm over the 0-150 mm range. They also had an official AliExpress store, so I purchased their SHAHE 5101L calipers. The 'L' suffix in the product code signifies wireless capability. That purchase was a year ago; this short review covers my findings since then. Look and Feel The calipers arrived in a sturdy, purpose-built plastic case. While the case is excellent quality, I rarely use it since the calipers are in near-daily use. In my experience, the calipers are as well-built as the Moore & Wright models I previously owned. The metal components slide smoothly, are well-machined, and feature a brushed finish. The plastic and front scale have a matte surface. The instrument feels great in the hand, and nothing has become loose over the year I’ve used the calipers. Overall, the 5101L is heftier than my old calipers. The electronics housing is substantial and made from thick, high-quality plastic. The battery door is secure and unlikely to get lost, as it slides in like a drawer and has a rubber seal. The locking screw has ample rotational travel before it could fall out. On the rear of the plastic body is a table with fraction-to-decimal conversions. I haven’t needed it, and while the text is quite small, it’s still readable thanks to clear black print on a thick metallic label that covers as much of the underside as possible. The label isn’t recessed but has remained intact after a year of use. The ergonomics are excellent - even when wearing gloves, the calipers are comfortable to operate. The buttons are clicky, with a spongy travel before the click is felt and heard. Personally, I preferred the softer press of the Moore & Wright calipers, but that’s just a matter of preference. Usability The device has its pros and cons. The LCD refreshes at four times per second, which is reasonably fast, though a speed closer to 8 Hz would be ideal. The digits are legible, but slightly thicker segments and squatter characters would enhance readability. Display contrast is acceptable and perfectly usable, though not exceptional. When powered on, the instrument always reads zero, regardless of the caliper’s actual position. Initially, this was frustrating, as I had to move the calipers to true zero and press the power button again to set the display correctly. However, I soon learned to power on the device only when fully closed, ensuring the displayed zero is accurate from the start. One user interface quirk is the somewhat cumbersome power-off process. You must hold the power button for a few seconds to cycle through menu items, then quickly press it again when ‘OFF’ appears. I can see why they did this; the design likely assumes most users will rely on auto power-off, especially since battery life is excellent - I haven’t replaced the original battery in a year. Still, as someone who prefers powering off manually, I find this extra step mildly inconvenient. Aside from that, as mentioned earlier, it’s actually a pleasure to use the calipers. The measured values match the Moore & Wright calipers each time I compare. Bluetooth Functions After contacting the manufacturer, I received a mobile app for the instrument. As expected, installing it requires adjusting settings to allow installation from outside the app store. Fortunately, because the calipers use standard Bluetooth Low Energy (BLE), it’s straightforward to monitor the protocol and create a DIY custom app with a bit of AI assistance (the link to this app is below). The custom app simply displays the measured value in large, clear digits (in millimeters), but adding inch conversion, or even nearest fractional values, would be easy. The wireless capabilities are demonstrated in this 2-minute video. www.youtube.com/watch Summary I was pleasantly surprised with these calipers. They are clearly well-made, and still look almost as good as new after a year of use. And I’m happy it’s all held together and no lost bits! The instrument matches the accuracy of my older calipers, carries an IP54 rating, and is easy to use. There are minor annoyances - for example, I wish the calipers would remember if Bluetooth continuous measurement mode was enabled, rather than requiring me to re-enable it through the menu each time. (According to the manufacturer, this cannot be configured remotely via BLE.) Still, sending a measurement to mobile devices is fast and straightforward with a single button press, as shown in the video. For anyone interested, I purchased from AliExpress a year ago, for £36, and total of £43 when shipping was included. Currently (March 2026), the 5101L is lower cost (£35, and £1 shipping fee) from the official store. The 'L' suffix model is the one with wireless. Regarding the custom app, it can be run by clicking here: SHAHE Caliper Tool , and the source code is on GitHub (it's just a single .html file). Thanks for reading the review.bluetoothblecalipersshahe5101Lcaliperhttps://community.element14.com/technologies/test-and-measurement/b/blog/posts/pico-scpi-lablib-now-has-configurable-usb-idsFri, 13 Mar 2026 15:22:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:595914cd-7373-4c70-85bb-a76ddb5fae53Jan CumpsMichael Stoops submitted pull requests to make a set of USB parameters configurable in your CMake file. What USB IDs can be configured? USB_VID USB_PID USB_MANUFACTURER USB_PRODUCT USB_SERIALNUMBER FW_VER_BCD FW_VER_STR Before this new functionality was introduced, these attributes were defined in the LabLib source code. They had the same values as those of the Pico SDK examples. When you want to commercialise a device, you need to set those to IDs that you license from the USB.org, and to your internal IDs. In the past, you needed to alter LabLib's source. You can now define these, in the build file (or from the command line). Setting the IDs In your CMake config file ( example from LabTool ), you can add a section with the defines. # set the USB IDs for this device target_compile_definitions(${CMAKE_PROJECT_NAME} PRIVATE USB_VID=0xCafe USB_PID=0x4000 USB_MANUFACTURER=0x01 USB_PRODUCT=0x02 USB_SERIALNUMBER=0x03 FW_VER_BCD=0x0100 FW_VER_STR="01.00" ) If you don't define (some of) those, the initial example values from the Pico SDK are used. link to all postspico_usbtmc_scpipicoUSBTMCPico SCPI labToolscpilabtool