627H21TBC1B MKS Instruments 627H Heated Baratron Pressure Transducer

627H21TBC1B | Heated Absolute Pressure Measurement

MKS Instruments 627H21TBC1B is a heated absolute pressure transducer from the 627H (600 Series).

This model measures absolute pressure across a 20 Torr full-scale range. Its sensor operates at a controlled temperature of 45°C.

The heated design helps maintain stable sensor temperature during pressure measurement. Vertical calibration supports installations that require a defined calibration orientation.

The instrument provides a 0 to +10 VDC analog output. It operates from a ±15 VDC power supply and uses an Inconel wetted construction.

Model Identification

• Manufacturer: MKS Instruments
• Model: 627H21TBC1B
• Product Family: 627H (600 Series)
• Instrument Type: Heated Baratron Absolute Pressure Transducer
• Measurement Range: 0–20 Torr absolute
• Sensor Temperature: 45°C controlled
• Calibration Orientation: Vertical
• Output Signal: 0 to +10 VDC
• Process Connection: 8 VCR Female

01 | Measurement Architecture and Performance

The 627H21TBC1B uses a heated Baratron measurement platform. It measures absolute pressure rather than gauge or differential pressure.

Measurement Parameter	Specification
Measurement Type	Absolute Pressure
Full-Scale Range	20 Torr
Accuracy	0.12% of Reading
Resolution	0.001% of Full Scale
Non-Linearity	Included in specified accuracy
Hysteresis	Included in specified accuracy
Non-Repeatability	Included in specified accuracy
Warm-Up Time	2 Hours
Calibration Position	Vertical

Measurement Accuracy: The specified accuracy is 0.12% of reading. This specification includes non-linearity, hysteresis, and non-repeatability.

Measurement Resolution: The stated resolution equals 0.001% of full scale. At 20 Torr, this corresponds to 0.0002 Torr.

Resolution describes the smallest specified measurement increment. It does not represent absolute measurement accuracy.

02 | Thermal Control and Measurement Stability

The sensor maintains a controlled temperature of 45°C. This heated configuration helps reduce measurement variations associated with sensor temperature changes.

Thermal Parameter	Specification
Controlled Sensor Temperature	45°C
Operating Temperature	15 to 40°C
Warm-Up Time	2 Hours
Zero Temperature Coefficient	0.002% FS/°C
Span Temperature Coefficient	0.02% of Reading/°C

Engineering Considerations:

• Allow the full two-hour warm-up period before critical measurements.
• Maintain ambient temperature within the specified operating range.
• Avoid rapid temperature changes around the instrument.
• Check zero stability after thermal stabilization.
• Evaluate span deviation when ambient conditions change.

The sensor temperature and ambient operating temperature describe different conditions. The 45°C internal setting does not change the specified 15–40°C ambient limit.

03 | Electrical Interface and Signal Integration

The transducer provides an analog voltage signal for pressure monitoring systems. Its electrical interface supports integration with compatible industrial measurement equipment.

Electrical Parameter	Specification
Power Supply	±15 VDC
Power Tolerance	±5%
Maximum Current	0.25 A
Analog Output	0 to +10 VDC
Minimum Load Impedance	>10 kΩ
Electrical Connector	15-Pin D-Sub
Connector Retention	Thread Locks
Trip Points	Not Available
Heater Status LED	Not Available

Analog Signal Interpretation

Assuming a linear 0–10 V output across the 0–20 Torr range:

• 0 V corresponds to 0 Torr.
• 2.5 V corresponds to 5 Torr.
• 5 V corresponds to 10 Torr.
• 7.5 V corresponds to 15 Torr.
• 10 V corresponds to 20 Torr.

Use the actual instrument transfer function when configuring the receiving system. Verify the output scaling before commissioning.

PLC and Data Acquisition Integration:

• Use a compatible voltage input channel.
• Confirm the input impedance exceeds 10 kΩ.
• Provide the required bipolar ±15 VDC supply.
• Verify signal common and grounding arrangements.
• Use shielded wiring where the installation requires it.
• Check electrical noise before adjusting measurement scaling.

04 | Process Connection and Wetted Construction

The pressure boundary uses Inconel wetted materials. The process connection features an 8 VCR female fitting.

Mechanical Parameter	Specification
Wetted Material	Inconel
Process Fitting	8 VCR Female
Internal Volume	6.3 cc
Overpressure Limit	45 psia (310 kPa) or 120% FS, whichever is greater
Diameter	3.15 in (80.0 mm)
Body Height	3.87 in (98.4 mm)
Stem Length	1.38 in (35.1 mm)

Installation Space: Allow sufficient clearance for the sensor body, stem, process fitting, and electrical connector.

Pressure Protection: The overpressure limit does not represent a normal operating pressure range. Avoid pressure excursions beyond the specified limit.

05 | Installation and Commissioning Procedure

Mechanical Installation

1. Confirm the mounting position matches the vertical calibration orientation.
2. Check the 8 VCR female connection against the process line.
3. Inspect sealing surfaces before connecting the pressure line.
4. Use compatible VCR sealing components.
5. Avoid excessive mechanical loading on the instrument body.
6. Keep the installation within the specified pressure limits.

Electrical Installation

1. Verify the bipolar ±15 VDC power supply.
2. Check supply polarity and voltage tolerance.
3. Inspect the 15-pin D-sub connector.
4. Secure the connector using its thread locks.
5. Connect the analog output to a suitable voltage input.
6. Verify signal common and grounding arrangements.

Commissioning Sequence

1. Apply the specified power supply.
2. Allow at least two hours for warm-up.
3. Confirm stable ambient temperature.
4. Check the zero-pressure reference under suitable conditions.
5. Apply known pressure points using a calibrated reference.
6. Compare the output voltage with the expected pressure.
7. Confirm the receiving controller displays the correct engineering units.

06 | Diagnostic Checks and Maintenance

Practical Troubleshooting Reference

Observed Condition	Recommended Inspection
No Analog Output	Check ±15 VDC supply, connector wiring, and receiving input.
Output Does Not Reach Expected Value	Verify pressure reference and analog scaling.
Zero Reading Drifts	Check warm-up completion and ambient temperature stability.
Unstable Pressure Display	Inspect pressure connections, grounding, and signal wiring.
Slow Stabilization	Check thermal stabilization and process pressure conditions.
Unexpected Calibration Deviation	Verify mounting orientation and calibration reference.

Maintenance Recommendations

• Inspect process fittings during scheduled maintenance.
• Check supply voltage before investigating measurement errors.
• Keep the electrical connector clean and secure.
• Record zero and span verification results.
• Use suitable reference equipment for calibration checks.
• Follow MKS service procedures for internal repairs.

This model has no trip points or heater status LED. Engineers should verify operating conditions through external measurements and system diagnostics.

07 | Application and System Integration

The 20 Torr absolute measurement range suits low-pressure monitoring applications. The analog output supports integration with compatible pressure monitoring systems.

• Semiconductor Equipment: Pressure monitoring in compatible process chambers and vacuum equipment.
• Vacuum Systems: Absolute pressure measurement within the configured range.
• Thin-Film Processes: Pressure feedback for suitable deposition equipment.
• Gas Delivery Systems: Pressure monitoring in compatible low-pressure gas lines.
• Industrial Instrumentation: Analog pressure measurement through PLC and data acquisition interfaces.

Application suitability depends on process gas compatibility, pressure conditions, installation design, and required measurement performance.

08 | Model Selection and Ordering Verification

Several configuration details determine whether this instrument matches an existing installation. Verify the complete model number before purchasing.

• Measurement Range: Confirm the required 20 Torr full scale.
• Measurement Type: Verify absolute pressure measurement.
• Heating Configuration: Confirm the 45°C sensor temperature.
• Calibration: Check the vertical calibration requirement.
• Output: Confirm the 0–10 VDC signal interface.
• Power: Verify the ±15 VDC supply availability.
• Connection: Confirm the 8 VCR female fitting.
• Material: Check Inconel compatibility with the process.

Ordering Tip: A matching 20 Torr range alone does not guarantee interchangeability. Compare the electrical interface, calibration orientation, heating configuration, and process connection.

09 | Compliance and Package Information

Compliance

• CE compliant.

Confirm the applicable declaration and documentation for the exact supplied configuration.

Package Contents

• 1 × MKS Instruments 627H21TBC1B Heated Baratron Pressure Transducer.
• Additional accessories and documentation depend on the confirmed order configuration.

Power cables, mating connectors, calibration certificates, and mounting accessories require separate confirmation.

10 | Technical FAQ

Q1: Why does the installation require vertical calibration orientation?

Calibration orientation defines the reference position for specified measurement performance. Mechanical orientation can affect pressure sensor readings in certain designs.

Install the instrument in its specified vertical position. If the equipment requires another orientation, consult MKS before installation.

Q2: How should engineers distinguish sensor resolution from system accuracy?

Resolution describes the smallest specified measurement increment. Accuracy describes how closely the measured value represents the actual pressure.

For this model, resolution is 0.0002 Torr. Its specified accuracy is 0.12% of reading.

PLC input resolution and signal noise can reduce the effective measurement resolution of the complete system.

Q3: What can cause an incorrect pressure reading after replacing the transducer?

Common causes include incorrect signal scaling, unsuitable mounting orientation, and incompatible power supplies.

Engineers should also check the 8 VCR connection and the receiving instrument configuration.

Compare the analog output against a calibrated pressure reference before changing controller parameters.

Q4: Why should engineers wait two hours before performing calibration checks?

The internal sensor uses controlled heating at 45°C. Its thermal condition needs time to stabilize after power-up.

Performing calibration checks too early can introduce misleading zero or span deviations.

Allow the specified warm-up period before evaluating measurement performance.

Q5: What should buyers verify when selecting this model for vacuum equipment?

First, confirm that 20 Torr absolute pressure covers the actual process operating range.

Next, verify the vertical calibration, 45°C heating configuration, and 0–10 VDC output.

Check the available ±15 VDC supply and 8 VCR female connection. Also confirm Inconel compatibility with the process media.

For replacement projects, provide the original nameplate photograph and equipment interface details before ordering.

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