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MKS 626B Baratron capacitance manometer
The MKS 626B01TDE is a Baratron® capacitance manometer. Its measuring principle is independent of gas type, which makes it widely used for vacuum control in semiconductor processes. The 626B series covers full-scale ranges from 0.1 Torr to 1000 Torr and outputs a 0–10 V analog signal directly to the process controller. Key selection points: full-scale range, heater temperature and vacuum fitting.
Model status (per MKS data): the 626C datasheet is marked DISCONTINUED; the current unheated equivalent is the 626D (0.1–1000 Torr, 0–10 VDC, 15-pin D-sub). Whether a 626B can be replaced directly by a 626D must be confirmed with the manufacturer — please send us the full model number and the equipment name.
Why capacitance manometers in semiconductor processes?
Vacuum gauges use several principles (thermal conductivity, ionization, capacitance). A capacitance manometer measures true pressure (force per area) and is not affected by gas type or composition. In CVD, PVD and etch chambers the gas composition changes constantly, so capacitance manometers give consistent readings across different process atmospheres.
626 / 627 / 628 series
| Series | Range (Torr) | Typical use | Heating |
|---|---|---|---|
| 626B | 0.1–1000 (0.1, 0.25, 1, 2, 10, 20, 100, 500, 1000) | CVD / PVD chamber pressure control, load locks | Unheated |
| 627 | 0.02–25,000 (current 627H) | High-vacuum processes, etch chambers, ion implantation | 45°C |
| 628 | 0.05–25,000 (current 628H) | Processes needing 100°C heating to prevent condensation | 100°C |
The ranges of the three series overlap; the main difference is the heater temperature.
Model code example
Taking 626B01TDE (MKS model code): 626B (series and version) · 01T (full scale 1 Torr) · D (vacuum fitting NW16-KF) · E (accuracy ±0.25% of reading). The 626 series is unheated, so there is no heater code; when ordering, the key items are full scale and vacuum fitting.
626B01TDE specifications
| Item | Details |
|---|---|
| Principle | Capacitance manometer |
| Full scale | 1 Torr (01 = 1 Torr) |
| Accuracy | ±0.25% of reading (typical) |
| Output | 0–10 VDC (analog) |
| Heating | Unheated |
| Electrical connector | 15-pin D-sub |
| Vacuum fitting | NW16-KF (code D; 8 VCR female is code B) |
| Power supply | ±15 VDC |
| Gases | Non-corrosive gases (N₂, Ar, He, etc.) |
Heated vs. unheated
Baratron heaters prevent process gases from condensing on the sensing diaphragm. When the chamber contains moisture or other condensable gases, deposits change diaphragm deflection and cause reading drift.
| Type | Series | Temperature | Use |
|---|---|---|---|
| Unheated | 626 | None | Inert gas, no condensation risk |
| Heated | 627 | 45°C | General CVD / PVD, light moisture |
| Heated | 628 | 100°C | ALD, high-moisture processes |
| Heated | 631 | 200°C | Corrosive precursors, high-temperature processes |
Replacement
Baratrons are wear items: after a period of use, diaphragm fatigue causes zero drift, and fabs typically replace them on a PM schedule. When replacing: (1) full scale must match, (2) heated and unheated models must not be mixed, (3) confirm the flange type (VCR / KF / CF).
Quick selection
| Step | Check | Choice |
|---|---|---|
| 1. Full scale | Where does the process working pressure fall? | Choose a full scale that puts working pressure at 10–90% of FS (626 / 627 / 628 ranges overlap) |
| 2. Heating | Condensable gases present? | Yes → 627 (45°C) or 628 (100°C); no → 626 (unheated) |
| 3. Fitting | Equipment flange? | VCR / KF25 / CF (confirm on the equipment side) |
When requesting a quote, please tell us: (1) the full model number (e.g. 626B01TDE), (2) quantity, (3) the equipment name (to check compatibility). If you only have a partial model number or the nameplate is missing, full scale + flange type can be used to identify the model. Units with the same full model number (range, fitting and accuracy codes) are interchangeable; if model numbers differ, check range, fitting and electrical wiring first.
Related: KEYENCE AP-C30W compound pressure sensor · Panasonic DP-101 vacuum pressure sensors · SMC ISE20A / ZSE pressure switches
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