Description
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | ZYGO Corporation |
| Product Model | ZMI-4004 |
| Series | ZMI 4000 Series |
| Product Type | Measurement Electronics Board |
| Measurement Axes | 4 per board |
| Board Format | 6U VME / VME64x |
| Position Resolution | 0.15 nm, double-pass configuration |
| Position Range | ±10.6 m |
| Maximum Velocity | ±2.55 m/s |
| Velocity Resolution | 18–22 bits, depending on digital filter settings |
| Maximum Acceleration | 100 g |
| Minimum Optical Power | >1.0 µW AC per axis |
| Maximum Optical Power | Approx. 76 µW AC per axis |
| Measurement Input | ST fiber optic, 20.0 ±16.1 MHz |
| Reference Input | ST fiber optic or HSSDC electrical, 20.0 MHz |
| Reference Outputs | 2 × HSSDC electrical, 20.0 MHz |
| Data Rate | Up to 10 MHz |
| Data Format | Parallel / VME high-speed serial |
| Maximum Boards | 16 boards / up to 64 axes |
| Power Requirement | 5 VDC +0.25/-0.125 V, 6 A max |
| Operating Temperature | 10–50 °C |
| Operating Humidity | 0–90%, non-condensing |
| VME Addressing | A24 |
| VME Data Transfer | D16 or D32 |
| Connectors | P1/P2, 160-pin DIN |
| Status Indicators | Measurement, reference, error and configuration LEDs |
The ZMI-4004’s four measurement channels are independent optical measurement inputs. The published specification identifies ST fiber-optic inputs, a 20.0 ±16.1 MHz measurement frequency range, and 20 MHz reference inputs. It also specifies a 25 ns time resolution and 37-bit two’s-complement position format.
Power is worth checking before putting an older board into a replacement chassis. The published 4004 specification calls for 5 VDC with a maximum current of 6 A, while cooling requirements increase with ambient temperature. At 30 °C, the specified typical airflow is 250 linear ft/min; at 50 °C, it rises to 600 linear ft/min.
ZYGO currently identifies the ZMI-4004 as a four-axis ZMI measurement board and lists the product under its ZMI measurement-electronics portfolio. The current ZYGO store identifies the corresponding SKU as 8020-0102-11.
Application Scenarios & Pain Points
At nanometer measurement levels, a replacement board cannot be validated by simply watching the VME LEDs turn green. Optical power, reference frequency, interferometer geometry, fiber condition, timing, and software configuration can all affect the final position value.
Typical Applications
- Precision Motion Stages: Four-axis measurement allows simultaneous monitoring of multiple displacement channels in a precision positioning system.
- Semiconductor Metrology: ZMI measurement electronics are intended for demanding position-metrology applications where sub-nanometer resolution is required. ZYGO describes its ZMI electronics as suitable for challenging precision-position applications.
- Closed-Loop Position Control: The high-speed displacement output can be incorporated into motion-control architectures where stage position must be measured independently of the actuator.
- Multi-Axis Interferometer Systems: Up to 16 units can be synchronized according to the published 4004 specifications, providing as many as 64 measurement axes.
Field Case:
An older VME-based metrology system may show a perfectly healthy host computer while one measurement axis suddenly reports an error. Before replacing the ZMI-4004, check the corresponding optical fiber, interferometer, laser reference, and measurement-channel LED. Swapping a known-good fiber between channels—where the system design permits it—can quickly separate an optical-path fault from an electronics fault.
ZMI-4004
Related Products
- ZYGO ZMI-4104 / 4104C — Four-axis measurement electronics from the newer 4100 family. ZYGO lists the 4104(C) alongside the 4004, but the two belong to different generations and should not be treated as automatic drop-in replacements.
- ZYGO ZMI-2400 — Earlier ZMI measurement board supporting one or two axes. Its published position resolution is 0.31 nm, compared with 0.15 nm for the 4004 in the specified double-pass configuration.
- ZYGO ZMI 7702 Laser — Compatible ZMI laser platform used to provide the optical reference for applicable ZMI measurement systems. It is part of the optical chain, not a substitute for the 4004 board.
- ZYGO ZMI 7714 Laser — Another ZMI laser option listed by ZYGO for its measurement-electronics architecture. Optical configuration must be checked before substitution.
- ZYGO ZMI 7724 Laser — ZMI laser platform associated with the measurement-electronics family. It supplies the optical source/reference required by the interferometer system.
- ZYGO ZMI-501A — Stand-alone two-axis measurement-electronics enclosure. It provides a different mechanical and system-integration format from the 6U VME 4004.
- ZYGO ZMI Go! — Compact modern ZMI electronics supporting up to four measurement channels, with EtherCAT and SSI interfaces. It is intended for a different control-system integration strategy than the legacy VME-based ZMI-4004.
- ZYGO ZMI Interferometers — Optical measurement heads that supply the displacement information processed by the 4004. The board cannot be evaluated independently from the appropriate interferometer and optical path.
- ZYGO Fiber Optic Cables — Used between the interferometer system and measurement electronics. ZYGO specifies ST-connector fiber cables for its ZMI systems; contamination or damage at these interfaces can produce measurement errors that resemble electronics problems.
The Engineer’s Guide: Field Pitfalls to Avoid
⚠️ Do Not Confuse Resolution With Guaranteed System Accuracy
The 0.15 nm figure is associated with the specified double-pass interferometer configuration. It does not mean that every complete machine will achieve 0.15 nm system accuracy.
How to avoid it: Check the interferometer geometry, laser stability, optical alignment, environmental conditions, and mechanical stage before using the board’s published resolution as a system acceptance criterion.
⚠️ Check the VME Power and Cooling
The 4004 specification calls for 5 VDC at up to 6 A. A VME chassis that can physically accept the card may still have inadequate power delivery or cooling.
How to avoid it: Verify the chassis power budget, 5 V rail voltage under load, airflow, and installed neighboring boards before commissioning. The published cooling requirements become more demanding as ambient temperature rises.
⚠️ Optical Input Problems Can Look Like Board Failure
The ZMI-4004 relies on optical measurement and reference inputs. Dirty ST connectors, damaged fibers, low laser output, or incorrect optical routing can produce measurement errors while the electronics remain functional.
How to avoid it: Inspect and clean optical connectors using the site’s approved procedure, verify reference and measurement signal presence, then test the suspect channel with known-good optical hardware.
Frequently Asked Questions (FAQ)
What is ZYGO used for?
The is a four-axis optical displacement measurement board used in ZYGO ZMI interferometer systems. It processes optical signals to generate high-resolution position and velocity measurements for precision motion and metrology applications.
What is the resolution of the ?
ZYGO’s published specification lists 0.15 nm position resolution for the double-pass interferometer configuration. A separate datasheet specifies 0.31 nm for a one-pass arrangement and 0.15 nm for a two-pass arrangement.
That distinction is important when comparing specifications from different system configurations.
How many axes does support?
One provides four measurement axes. The published specification allows up to 16 boards, corresponding to as many as 64 measurement axes, subject to VME and system-population limitations.
Is a VME board?
Yes. It is a 6U VME/VME64x measurement board. The documented VME interface supports A24 addressing and D16/D32 data transfers, with P1 and P2 160-pin DIN connectors.
This makes the host chassis and backplane configuration part of the replacement assessment.
Can ZMI-4104C replace ?
Not automatically. Both provide four measurement axes, but the 4004 belongs to the ZMI 4000 family, while the 4104/4104C belongs to the 4100 family. ZYGO lists them as separate measurement-board products.
For a legacy system, verify software, host VME configuration, laser compatibility, optical inputs, timing requirements, and required measurement performance before approving a substitution.
What is the ZYGO part number for ?
ZYGO’s current product store identifies the ZMI 4004 Measurement Electronics with SKU 8020-0102-11.
Older boards may carry different internal or historical identification numbers, so the PCB label and serial number should still be photographed during procurement.
What should I request when buying a refurbished ?
Ask the supplier to provide:
- Actual front and rear photographs
- identification
- Full part/assembly number
- Serial number
- PCB revision
- VME P1/P2 connector inspection
- 5 VDC power test
- VME initialization test
- Four-channel measurement test
- Reference-input test
- Optical signal test
- Known-good interferometer/laser verification
- Position-data stability test
- LED/status verification
- ESD-safe packaging
- Warranty terms
A power-on test alone is weak evidence for this board. The useful acceptance test is four-channel optical measurement with a known-good ZMI laser/interferometer setup, followed by verification of stable position output. ZYGO’s own documentation treats the 4004 as part of a complete optical measurement system rather than an isolated conventional I/O card.
