How to Verify Precision in Motion Control & Optical Systems: A 5-Step Quality Checklist

Who This Checklist Is For

If you're specifying a Zeiss microscope for ophthalmology, choosing an encoder for a motion control system, or trying to figure out if thermal cameras can actually see through glass—this is for you. I'm a quality compliance manager at an industrial optics firm. I review roughly 200+ items per year—microscopes, CMM fixtures, sensors, you name it. Over the past four years, I've rejected about 12% of first deliveries due to spec mismatches. This checklist is what I actually use.

It covers five steps. Each one has saved me from at least one expensive redo.

Step 1: Verify the Baseline Reference (Not Just the Spec Sheet)

Everyone checks the spec sheet. Few people check whether the spec sheet is correct for their use case. I learned this the hard way.

When specifying a Zeiss microscope for ophthalmology, the brochure might say "magnification up to 40x." Sounds great. But is that at the eyepiece or on the monitor? In our Q1 2024 audit, we received a batch where the quoted magnification was only achievable with an additional adapter module—not included. The vendor assumed we knew. We didn't.

Here's my rule: Ask for the exact measurement conditions.

• For microscopes: objective magnification vs. total system magnification
• For encoders: resolution vs. accuracy (they're not the same)
• For thermal cameras: is the "through glass" claim valid for your glass type? Double-glazed vs single-pane changes the answer

Step 2: Look for Quantitative Evidence, Not Marketing Claims

I once approved a motion control encoder because the datasheet said "high precision." That phrase means nothing. Encoder price can vary 5x between a 12-bit and 20-bit model, yet both datasheets say "high precision."

When I implemented our verification protocol in 2022, I started requiring three things:

1. Quantified error margins (e.g., ±0.01° for angular encoders, not "excellent accuracy")
2. Test environment conditions (temperature, humidity—affects optical systems heavily)
3. Reference standard used (was it calibrated against a national standard?)

For sensors for motion control, I now request the ISO 10360-2 compliance report. If the vendor can't provide it, I move on. That single change has cut our field failure rate by about 34%.

Step 3: Check Interoperability with Existing Systems

This is the step most people skip. They verify the sensor works. They don't verify it works with their controller.

I once sourced an encoder that was technically perfect—20-bit resolution, IP67 rating, good price. But its output format (SSI) wasn't compatible with our existing PLC. The integration cost added $4,200 to a $18,000 project. On a 50,000-unit annual order, that's not a rounding error—it's a justification failure.

When evaluating encoder price, always include compatibility verification in your total cost calculation. It's not just about the unit cost. It's about what it takes to make it work.

Step 4: Test the Edge Cases—Especially the "Impossible" Ones

Everyone tests the normal operating conditions. No one tests the edge cases until something breaks.

A common question I get: "Can thermal cameras see through glass?" The short answer is: it depends. Standard thermal cameras (LWIR, 8–14 μm) cannot see through standard glass—glass is opaque in that range. But there are exceptions:

• Some specialized systems use MWIR (3–5 μm) with specific window materials
• Flir offers models with radiometric calibration that can see through germanium or zinc selenide windows—not soda-lime glass

I only believed this after ignoring the warning on a project. We specified a standard thermal camera for a furnace inspection window. The camera returned a uniform black image. The window was standard glass. That cost us a $4,500 redo and delayed the launch by three weeks.

Now our protocol includes: Request a side-by-side test under your actual conditions. Not a lab simulation. Your glass. Your camera. Your light source.

Step 5: Evaluate the Soft Factors (Documentation, Support, Consistency)

This sounds vague, but I'll make it concrete. I rank vendors on three subjective criteria:

1. Documentation clarity—Can I find the calibration date within 30 seconds of opening the manual?
2. Response time on spec questions—If they take four days to answer, that's a preview of support delays
3. Consistency across deliveries—I request three sample units from different production lots. If Zeiss provides serial-numbered units with traceable calibration, I know I'm dealing with a mature quality system

I once chose a vendor with better documentation over one with a slightly lower encoder price. The documentation vendor's defect rate was 0.3% vs. 1.8%. On a 50,000-unit order, that's 750 fewer failures. The documentation cost nothing extra.

Common Mistakes to Avoid

• Assuming "compatible" means "plug-and-play"—It rarely does. Electrical and mechanical compatibility are separate checks.
• Trusting a single datasheet value—Cross-reference at least two independent sources. For Zeiss microscopes, check both the product page and the technical manual.
• Ignoring firmware versions—A sensor's performance can change significantly between firmware releases. I once found a 15% accuracy difference between v2.1 and v2.3 of the same encoder model.
• Assuming thermal imaging is universal—Can thermal cameras see through glass? Not standard glass. But they can see through thin plastic, smoke, and fog. Know the difference for your application.

If you follow these five steps, you'll catch at least 80% of spec mismatches before they become project delays. I've used this checklist for three years, across hundreds of items. It's not perfect—but it's the closest thing I've found to a reliable filter.