Tektronix Function Generators, 4-Channel Oscilloscopes, and Test Equipment: A Buyer's FAQ

I manage office and equipment purchasing for a 45-person automation engineering firm. That means I order test equipment—roughly $300,000 a year across 12 vendors—and I report to both operations and finance. When I took over in 2020, I barely knew what a function generator did. After five years and a few expensive mistakes, I know which questions are worth asking before I push the order through.

Here are the questions I keep answering, both for our team and for vendors:

• Which Tektronix function generator do we actually need?
• Why does every engineer ask for a Tektronix 4 channel oscilloscope?
• What does an HVAC clamp meter do that a regular meter doesn't?
• What is a 436 micrometer used for?
• Are insulation testers and meggers the same thing?
• Should I buy original Tektronix probes or save money on third-party ones?

1. Which Tektronix function generator do we actually need?

The short answer is: it depends on whether you need standard waveforms or arbitrary ones. For sine, square, and triangle waves, a Tektronix AFG1022 is often enough. If you need to create unusual or custom waveforms, you need something like an AFG31000. The numbers in the model name tell you bandwidth and sample rate, but the bigger decision is arbitrary waveform capability.

People think higher frequency is always better. Actually, what matters is whether the signal can be cleanly reproduced in your test setup. For many of our bench tests, 25 MHz is plenty. What I mean is: the engineers aren't going to get value from a 250 MHz generator if the device they are testing only responds to audio-frequency signals. Paying for unused frequency capability is money we can't spend on better probes.

Check Tektronix's product page before you order. According to the Tektronix AFG31000 series page (accessed January 2025), the higher-cost units add deeper memory and arbitrary waveform generation. If no one on the team says 'I need to create a custom waveform,' save the budget.

One more thing: count the outputs. A two-channel function generator is useful when you need a clock and a data signal at the same time. If you only need one output, a single-channel unit may be enough. But the price difference is not as large as you'd think, so most teams here ask for two channels.

2. Why does every engineer ask for a Tektronix 4 channel oscilloscope?

Because modern circuits talk to each other. You might need to see the input signal, the output, and a control signal at the same time. With two channels, you can't do that unless you trigger on one signal and miss the relationship. A four-channel scope isn't just 'two more inputs.' It is the difference between seeing a serial bus decode while watching the enable pin and trying to debug blind.

The numbers said the 2-channel model would save us about $1,150. My gut said to go with the 4-channel, because previous 'we'll work around it' choices came back to bite us. I went with the 4-channel. Three months later, a tech was decoding an SPI bus while monitoring the power supply ramp. Every channel was in use. The $1,150 saving would have cost us at least a week of waiting for an available scope from another lab.

If you're ordering a Tektronix, look at the 4 Series MSO for high-end work or the TBS2000B if you're mostly looking at lower-speed signals. In my experience, the 4-channel version is the safer default for a mixed-signal lab.

Also, don't confuse four analog channels with mixed-signal channels. The Tektronix 4 Series MSO has optional digital input channels. That's a different spec. If the team expects to decode 16 digital signals, order the logic probe as well. I learned that the hard way when a delivery arrived with no way to connect the digital channels.

3. What does an HVAC clamp meter do that a regular meter doesn't?

First, to be transparent: Tektronix doesn't make the HVAC clamp meters we buy. That's fine. The purchasing logic is still the same. An HVAC clamp meter is a clamp meter optimized for motors, compressors, and things that draw big inrush current. You clamp it around one conductor, and it measures current without breaking the circuit. The 'HVAC' label usually means it has a low-pass filter and an inrush mode, which stop variable-frequency drive noise from making readings jump all over the place.

People think an HVAC clamp meter is a specialized tool that only works on air conditioners. Actually, it's just a clamp meter with features that happen to be useful for HVAC. It will work on other 500 V-or-less power circuits too. The important specs are the safety category (CAT III 600 V is a good starting point) and the inrush function. A cheap meter without a low-pass filter can show ghost readings on a motor drive.

If you already own a standard clamp meter, check whether it has a low-pass filter. On a motor drive, an unfiltered reading can be off by 20 percent or more. That is the real difference, not the brand name on the side.

4. What is a 436 micrometer used for?

When I first saw '436 micrometer' on a request, I assumed it was a niche tool with a strange name. It's actually simpler than that. A 436-series micrometer is a mechanical outside micrometer, usually with a 0-1 inch measuring range and 0.0001 inch resolution. It looks like a C-clamp with a fine screw. We use it to measure wire gauge, connector pin diameters, and shim stock thickness.

The thing I almost got wrong was not the micrometer itself—it was the ratchet. A micrometer without a ratchet or friction thimble depends on how hard the operator turns it. Too tight and the part is squeezed out of shape. Our metrology team caught that before I ordered. If your team is reporting measurements to a customer, also make sure you buy a calibrated unit with a certificate. An uncalibrated micrometer is just a precision-looking paperweight.

Also decide if you need a digital readout. For rapid inspection, digital is easier to read, but mechanical micrometers never run out of battery. If the team is logging data into a spreadsheet, digital with data output saves time.

5. Are insulation testers and meggers the same thing?

Sort of. This is one of those cases where a brand name becomes the generic word for an entire category. Megger is a registered trademark for insulation resistance testers. People say 'megger it' the way they say 'Kleenex' when they mean any tissue. So the correct comparison is not insulation tester versus megger; it's insulation tester versus the Megger brand. According to Megger's website, the word is a registered trademark, but that doesn't stop people from using it generically.

An insulation tester applies a DC voltage between conductors and the insulation, then measures how much current leaks through. The result is in megohms. If the reading is low, the insulation is weak. The buying decision should be based on the test voltage you need: 250 V, 500 V, or 1000 V for most motor and cable work. Higher voltage models cost more.

I approved our first insulation tester and immediately second-guessed the price. Did we need the high-voltage version? It turned out the motor test spec required a 1000 V range, and the cheaper 250 V model would have failed the acceptance criteria. The extra cost wasn't for the name. It was for the output voltage range.

One more note: don't assume a higher test voltage is always safer. Too much voltage can damage sensitive insulation. The spec should always come from the electrical engineer, not from the sales brochure.

6. Should I buy original Tektronix probes or save money on third-party ones?

I get why people look at the price difference. A Tektronix passive probe can cost several hundred dollars, and a generic one is a fraction of that. But the probe is part of the measurement. A probe with the wrong capacitance rating can load the circuit and turn a clean waveform into a rounded mess. We once had to redo a week of validation tests because a third-party probe introduced enough delay to change the timing measurement.

That said, you don't need to OEM everything. For BNC cables, decent third-party cables work fine. For passive probes, I match the bandwidth to the oscilloscope. According to Tektronix's probe selection guide (accessed January 2025), a passive probe's bandwidth should be at least equal to the scope's bandwidth. We standardize on Tektronix passive probes with 500 MHz bandwidth for our 4-channel scopes. Current and differential probes are another case where the original is worth it, mainly because of the amplifier interface and safety rating.

Active probes are the other trap. The amplifier on a Tektronix active probe is usually powered by the scope's proprietary interface, so a cheap non-OEM active probe won't connect in the same way. For passive probes, the choice is less risky, but still check the input capacitance match.

If you're ordering a Tektronix function generator, don't forget the BNC cables and the right adapters. That's where I saved money without hurting measurements.

7. What other hidden costs should I plan for?

Three things: calibration, accessories, and freight. A calibration certificate for a Tektronix oscilloscope or function generator is not bundled unless you ask. If your company is ISO 9001 or reports to a customer, budget for it. Otherwise you will be calling the lab back two days after delivery and paying an additional fee for a rush certificate.

Accessories are the second budget-buster. In 2023, we ordered a scope with standard passive probes, but the project also needed a differential probe. The differential probe cost about 35 percent of the scope's price. Nobody had flagged it because it was not in the quote. Now I ask the requesting engineer: what exactly will be measured, and what probe does it need? That one question has saved us more than any vendor discount.

Freight may seem minor, but oversized instruments use freight carriers and liftgate service. On one order, the delivery quote did not include residential-style access because the building has a loading dock. The carrier charged an extra delivery fee. Now I confirm the dock and liftgate in the purchase notes.