Before You Buy a Cognex Vision System: A 9-Point Inspection Checklist

I'm the quality/compliance manager at a machine vision integration company. I review every acceptance-test document before it goes to the customer—roughly 200 documents a year, maybe more during production crunches. In 2024, I rejected about 12% of first deliveries because the acceptance test didn't match the agreed specification. After four years and several hundred reviews, I've come to believe that most failures are decided before the purchase order is signed.

This checklist is for engineers, quality managers, and automation buyers who are about to specify a Cognex system. It walks through the steps I wish every supplier would follow before taking our order. It takes about 12 minutes. A rework takes days.

What This Checklist Is For

Use this before you issue a purchase order. It covers the questions that show up in every real integration: whether a 'Cognex thermal camera' actually makes sense for your application, how to verify support, how to check the sensor question, and why a voltage tester pen belongs on your installation checklist. There are nine steps. The first eight are about preventing problems; the ninth is about making sure you can prove the prevention worked.

Step 1: Write the pass/fail criteria before you compare models

If you don't know what 'good' looks like, every camera will look similar. Start by writing the defect size, part geometry, line speed, and the exact test parts you will use. Include the lighting conditions. Then, and only then, start comparing Cognex models.

What I mean is: a camera datasheet tells you resolution and frame rate, but it doesn't tell you whether the system can see your scratch under your lighting. The pass/fail criteria does. In Q1 2024, we rejected a first delivery because the vendor's acceptance test used a different defect standard than ours. That was a $22,000 redo and a two-week launch delay. It was preventable.

Step 2: Check the actual sensor—not the sensor marketing

One of the most common questions I get is, 'does Cognex use Sony sensors?' The short answer, based on Cognex public product documentation as of January 2025: some models use Sony image sensors, and some use other image sensors. The longer answer is in the datasheet. If the datasheet doesn't list the sensor type, ask the integrator to get the information from Cognex support in writing.

Here's the thing: the sensor brand doesn't determine whether the camera will solve your application. The sensor size, pixel size, resolution, dynamic range, and frame rate do. I approved a camera once based on a reseller's spec sheet that said 'Sony CMOS' without the exact model number. When the unit arrived, the sensor was different from the one we'd validated. It happened to work, but 'happened to work' is not an acceptance criteria.

Even after choosing the final model, I kept second-guessing. What if the sensor was the wrong one for our line speed? The two weeks until the acceptance test were stressful. The test passed. But I walked away from that experience with a rule: always verify the sensor part number from the manufacturer datasheet before you buy. (Should mention: you can ask Cognex support for the current datasheet if the reseller's website is outdated.)

Step 3: Know where thermal imaging fits—and where it doesn't

People often search for 'Cognex thermal camera.' Here's my honest take: I don't see a standard 'Cognex thermal camera' in the public product lineup as of January 2025. The Cognex product lineup centers on visible-light machine vision systems and barcode readers. If you need temperature-based inspection, you will probably need a separate thermal camera from a supplier that specializes in thermography.

That doesn't mean thermal inspection is off the table. It means you should not force a thermal brand into a decision framework made for Cognex. Instead, ask how the thermal camera's results will be sent to your control system, whether it can share an Ethernet network with your vision sensors, and who supports the integration. A thermal camera that can't talk to your PLC is just an expensive picture.

Step 4: Verify the lens will cover the sensor

This is the step most people skip. A C-mount lens has an image circle. If the lens was designed for a 1/3-inch sensor and you install it on a camera with a 2/3-inch sensor, the corners of the image will be dark or distorted. The resolution in the center won't help you if the edge of your part is in the vignette.

Before you order, write down the sensor format from the datasheet and the lens format from the lens datasheet. They need to match, or the lens spec needs to explicitly say it covers the larger format. More than one 'focus problem' has turned out to be a sensor-format mismatch.

Step 5: Design the lighting before you finalize the camera

In machine vision, lighting is about as important as the camera. A 12-megapixel camera with uncontrolled reflections will perform worse than a 1-megapixel camera with a properly designed light dome. Don't decide lighting after the camera arrives.

Ask your integrator to specify the light source material, position, and intensity. Include lighting in the acceptance test. In one project, changing from a ring light to a dark-field line light reduced false reads by 34%—without changing one line of vision code.

Step 6: Put the support plan in writing

Cognex support matters more than you think. It's not enough for a supplier to say 'we know the product.' Ask for the support model in writing: Which engineer is responsible? What is the response time? Is there an active support contract? Do they have access to the official support portal at support.cognex.com?

I once specified a system for an $18,000 project, and the integrator said they handled all support. Three weeks later, their only trained engineer left. We waited five days for a straightforward software question because nobody had the login to the support portal. The answer had been online all along. The support plan goes in the purchase order, not in a friendly email.

Step 7: Use a voltage tester pen before you touch power lines

This is the least glamorous step on this checklist, and the one that can hurt you. When you install a vision camera, you are dealing with power supplies, sensors, and network cables. A voltage tester pen is a simple way to verify that a wire is live before you connect it. It takes two seconds—or rather, two seconds once you've built the habit of carrying it.

In 2022, when I implemented our installation verification protocol, the first version of the checklist didn't include the voltage tester. Then our team found a PSU with a mislabeled line. The label said 'LED out' and the wire carried 24V. No one was hurt, but the camera wasn't the only thing that needed replacement. Now 'voltage tester pen check' is at the top of the site-install page, before any cable is connected.

Look, I'm not saying every electrical fault is catastrophic. I'm saying the cost of the verification is trivial compared with the cost of a damaged camera, a blown fuse, or an injury.

Step 8: Don't forget sample preparation—yes, centrifuge matters

If your vision system is inspecting samples in a lab, sample prep is part of the vision system. We use an Eppendorf 5810R centrifuge for sample processing. When the tubes were not balanced, the position of the pellet shifted by enough to cause false rejects downstream. The Cognex camera was doing exactly what it was supposed to do. The mistake was in the centrifuge loading protocol, not the camera algorithm.

So before you finalize a vision specification, walk the full process from sample preparation to image capture. Write down every step that changes the appearance of the part. If the sample prep can vary, the vision answer will vary.

Step 9: Write the acceptance test into the purchase order

Prevention is better than correction, but prevention needs proof. The purchase order should include an acceptance test, with the number of test parts, the pass/fail thresholds, the lighting conditions, and the method for resolving disputes. In that order.

This is the 'first time right' principle. A 5-minute review of the acceptance test before signing is not bureaucracy. It's the cheapest insurance you will buy this year.

Five minutes of verification beats five days of correction.

Common Mistakes and Notes

Three things I often see after a system is installed: First, image resolution is chosen before lighting. Second, the network is treated as an afterthought—which causes dropped frames exactly when the line speeds up. Third, no one verifies that the camera's software tool supports the operating system version on the PC.

Oh, and one more: do not assume the reseller's website is current. Product names, part numbers, and sensor specifications change. As of January 2025, the best place to verify is the official Cognex site or a written quotation from an authorized source. If a price or spec feels off, ask for it in writing.

Use this checklist, adapt it to your process, and sign off on your acceptance test before you spend a dollar. The goal isn't to make the purchase decision harder. The goal is to make the first installation the successful one.