TTR 101 Vacuum Gauge Troubleshooting Guide

Leybold THERMOVAC TTR 101 Vacuum Transmitter: A Complete Guide to Selection, Installation, Debugging, and Troubleshooting

Introduction: When your vacuum measurement requires high precision and wide range

Accurate measurement of vacuum pressure is the core of process control in semiconductor, coating, freeze-drying, analytical instruments, and research laboratories. The traditional Pirani vacuum gauge performs well in the low vacuum range (<1 mbar), but lacks accuracy near atmospheric pressure; Although capacitive thin film vacuum gauges have high accuracy and are independent of gas types, their measurement range is limited and the cost is high. Leybold's THERMOVAC TTR 101 series integrates Pirani sensors and capacitive thin-film sensors into the same transmitter, achieving wide range and high-precision measurements from 5 × 10 ⁻⁵ mbar to 1500 mbar. It meets the digital requirements of modern vacuum systems through logarithmic voltage output (0-10.23 V) and optional switch output (SP1, SP2) or Profibus interface.

This article is based on the TTR 101 series operation manual, providing a detailed technical guide from product selection, technical specifications, installation wiring, gas type correction, set point adjustment, troubleshooting to maintenance and calibration, to help engineers quickly master the use and replacement of the transmitter.

Overview and Selection of Product Series

The TTR 101 series includes three sub models to meet different application requirements:

Model Part Number Example Switch Function Interface Display

TTR 101 230 350 V01 (KF16)/230 351 V01 (NPT) No analog quantity+optional identification resistor (with display version suffix)

TTR 101 S2 230 352 V01 (KF16)/230 353 V01 (NPT) 2-channel solid-state relay analog+identification resistor+switch output optional

TTR 101 PB 230 358 V01 (KF16) 2-channel (via Profibus) Profibus DP no display (via bus communication)

All models use a combination sensor (Pirani+capacitive film) with a measurement range of 5 × 10 ⁻⁵~1500 mbar. Vacuum connection options include DN 16 ISO-KF (quick release flange) or ⅛ "NPT thread.

Selection suggestion:

Only analog output is required (such as connecting to Graphix, Display, or Center controllers), select TTR 101.

On site switch control is required (such as interlocking and alarm), choose TTR 101 S2.

Need to connect to Profibus DP network, select TTR 101 PB.

Core technical parameters and accuracy

2.1 Measurement principle and scope

There are two sensors inside TTR 101 that always work:

Diaphragm capacitive sensor: covering 10~1500 mbar, independent of gas type, with high accuracy.

Pirani sensor (thermal conductivity type): covers 5 × 10 ⁻⁵~1 mbar, and needs to be adjusted according to changes in gas type.

Crossover range: 1~10 mbar, two signals are fused proportionally.

2.2 Accuracy (N ₂ calibration)

Pressure range accuracy

5 × 10 ⁻⁴~1 × 10 ⁻³ mbar ± 50% reading

1 × 10 ⁻ ³~100 mbar ± 15% reading

100~950 mbar ± 5% reading

950~1050 mbar ± 2.5% reading

Note: The accuracy is lower in the Pirani lower limit region (<10 ⁻ ³ mbar), but this region is usually used to determine rough vacuum or extreme vacuum, and the absolute error is acceptable.

2.3 Repeatability

The repeatability of readings is ± 2% within the range of 1 × 10 ⁻ ³ to 1100 mbar.

2.4 Output signal

Voltage range: 0~+10.23 V

Measurement signal range:+0.61~+10.23 V (corresponding to pressure 5 × 10 ⁻⁵~1500 mbar)

Fault signal: 0 V (default)

Voltage pressure relationship: logarithmic characteristic, 1.286 V/decade

Output impedance: 2 × 4.7 Ω, short circuit protection

Load impedance:>10 k Ω

Response time:<30 ms

2.5 Power Supply and Power Consumption

Supply voltage: 14.5~30 V DC (recommended 24 V DC)

Maximum power consumption: ≤ 2 W

Has reverse polarity protection

2.6 Switching output (S2 and PB models only)

Type: Solid state relay (optocoupler)

Setting range: 5 × 10 ⁻⁵~1500 mbar

Delay: Threshold 10% (programmable)

Switch characteristics: Low Trip Point (default) or High Trip Point (default)

Contact capacity:<30 V AC/DC, ≤ 0.3 A resistive load

Response time:<30 ms

2.7 Environment and Machinery

Working temperature:+5~+60 ° C (with display version up to 50 ° C)

Storage temperature: -40~+70 ° C

Baking temperature: up to 120 ° C (only sensor part, electronic unit needs to be removed)

Protection level: IP40 (after installation)

Shell material: stainless steel sensor+plastic electronic unit

Weight: Approximately 200 grams

Installation and mechanical connection

3.1 Installation direction and position

The transmitter can be installed in any direction. To prevent condensation and particles from entering the measurement chamber, it is recommended to adopt a horizontal to vertical upward installation posture.

If using seals with centering rings and filters, ensure that the filter mesh is clean.

After installation, the buttons (used to adjust zero/atmospheric pressure and set point) should be accessible, so there should be reserved operating space.

3.2 Grounding and Electromagnetic Compatibility

Key requirements:

The transmitter must be reliably grounded through a vacuum chamber (in accordance with EN 61010 protective grounding requirements).

For KF flanges, use conductive metal clamping rings (instead of plastic rings) to ensure electrical continuity.

The single end of the cable shielding layer is grounded (through the connector housing), and the other end is suspended.

The power supply common terminal (GND) should be directly connected to the protective ground at the power source.

Use differential measurement input (separate wiring for signal ground and power supply ground).

The potential difference between the power supply ground and the casing is ≤ 18V (overvoltage protection).

3.3 Electrical Connection (8-pin FCC 68 connector)

Pin signal description

1 Power supply++14.5~30 V DC

2 Power Supply GND Common Terminal

3 measurement signals/SP1, SP2 0~10.23 V or threshold output

4 transmitter identification 71.5 k Ω to GND

5 signal public measurement signal return

6,8 Relay SP2 normally open contact (com)

7,8 Relay SP1 normally open contact (com)

Note: When the<SP1>or<SP2>button is pressed, the measurement signal output will be temporarily suppressed and replaced with the current set threshold voltage (for monitoring). This operation may cause the controller to malfunction, and it is necessary to confirm safety before operating.

Gas type correction

TTR 101 is independent of gas type and does not require correction within the range of 10~1500 mbar (capacitive sensor). In the low-pressure range dominated by Pirani (<1 mbar), the relationship between indicated pressure and actual pressure depends on the thermal conductivity of the gas.

The manual provides a calibration factor table (for transmitters calibrated for air):

Gas calibration factor C, actual pressure=C x indicated pressure

He 0.8 

H₂ 0.8 

Ne 1.4 

Air, O ₂, CO, N ₂ 1.0

Ar 1.7 

CO₂ 1.7 

Kr 2.4 

Water vapor 2.4

Xe 3.0 

Freon 12 3.0 

For example, when measuring argon gas (Ar), if the transmitter displays 1 × 10 ⁻³ mbar, the actual pressure is 1.7 × 10 ⁻³ mbar. When precise measurement of non air/nitrogen media is required, this correction must be applied.

Operation and Display

5.1 LED indicator light

<ST>(Status): Green=Measurement Mode; Red or flashing red=malfunction; Extinguish=no power supply.

<SP1>/<SP2>: Green=relay closed; Off=relay disconnected.

5.2 LCD display (with display model)

Display the pressure value (Scientific notation, such as 1.2E-3 mbar).

Display the set value in parameter mode.

The red display indicates an error.

5.3 Parameter Mode and Setpoint Adjustment

Press the<SP1>or<SP2>button (using a needle tool, diameter ≤ 1.1 mm), the transmitter enters the switch function mode, and the measurement signal output is temporarily replaced with the current threshold voltage. The LCD displays the threshold and flashes<S>. Press the same button again to change the threshold (increase upwards, long press to change direction). Release the button for more than 5 seconds, the new threshold will be saved and exited.

Warning: This operation will change the measurement signal output, and if the signal is used for process control, it may cause misoperation. Be sure to confirm safety before operating.

5.4 Switch characteristics

Low Trip Point (default): When the pressure is below the threshold, the relay closes and the LED lights up.

High Trip Point: The relay closes when the pressure exceeds the threshold.

Delay: 10% of the default threshold, which can be modified through Profibus programming.

Calibration and Adjustment

TTR 101 is calibrated at the factory. Long term use or pollution may cause zero drift, and it is recommended to regularly (such as annually) adjust the zero point.

6.1 Atmospheric pressure adjustment (ATM adjustment)

Install the transmitter on the vacuum system and run it on power for at least 10 minutes.

Ensure that the system is vented to atmosphere (pressure ≈ 1000 mbar).

Short press the<ADJ>button once with a needle. The Pirani sensor will be adjusted to 1000 mbar (default).

6.2 High Vacuum Adjustment

Extract the vacuum system to<10 ⁻⁵ mbar (pressure much lower than 5 × 10 ⁻⁵ mbar).

Wait for at least 2 minutes to stabilize the pressure.

Press the<ADJ>button with a needle (long press or specific operation, not clearly distinguished in the manual, usually the same button as ATM, identified by pressure). The transmitter automatically adjusts the zero point to 5 × 10 ⁻⁵ mbar.

If the output signal displays ≈ 4.85 × 10 ⁻⁵ mbar (or corresponding voltage), the adjustment is successful; Otherwise, repeat.

Attention: Before adjustment, it is necessary to ensure that the vacuum system has been pumped to extremely low pressure, otherwise it may introduce erroneous offset.

Troubleshooting

7.1 Common Problems and Countermeasures

Possible causes and solutions for the phenomenon

The output signal is always<0.1 V, and the<ST>red sensor cable is damaged or connected incorrectly; No power supply inspection cable; Measure the supply voltage

<ST>The red light is always on, but the output is normal. The transmitter is in an undefined state. Power off for 5 seconds and restart (reset)

<ST>The red light is always on, and the output is abnormal. Pirani sensor is damaged and replaced (see 7.2)

<ST>Red is always on, abnormal output. Check for poor contact between electronic unit and sensor connection

<ST>The red constant light capacitive sensor is damaged and needs to be replaced

<ST>Red constant on EEPROM error, power off and restart. If it still exists, repair is required

<ST>The red constant light electronic unit is incompatible with the sensor. Replace the sensor or the entire transmitter

Continuous low output signal. Optical window or sensor contamination. Clean or replace sensor

The switch value does not operate and the set point is incorrect; Improper hysteresis setting, readjust SP1/SP2; Check the triggering mode of high and low points

7.2 Testing Pirani Sensor (Filament)

If you suspect a Pirani sensor malfunction, remove the sensor (see 7.3) and measure the corresponding pin on the electronic unit side with an ohmmeter (as shown in the manual):

Normal resistance: 40 ± 1 Ω

Pollution or partial short circuit: ≥ 40 Ω (may be higher)

Pollution or partial open circuit: ≤ 40 Ω

Filament burnout: ∞

Any situation exceeding 40 ± 1 Ω requires replacement of the sensor and cannot be repaired.

7.3 Steps for replacing sensors

Remove the transmitter from the vacuum system (see next section).

Use a hex wrench (AF 2) to loosen the hex socket screw between the electronic unit and the sensor.

Pull the sensor out of the electronic unit without twisting.

Insert a new sensor (also without twisting) and tighten the screw (torque of approximately 0.5 Nm).

Attention: After replacing the sensor, it is necessary to perform atmospheric pressure adjustment and high vacuum adjustment again.

Precautions for dismantling and returning to the factory

8.1 Disassembly steps

Release the vacuum system to atmospheric pressure.

Turn off the transmitter power.

Disconnect the sensor cable.

Remove the transmitter from the vacuum system and immediately install the protective lid.

8.2 Pollution Declaration

If the transmitter has been in contact with hazardous substances (radioactive, toxic, corrosive, biological hazards, etc.), a Declaration of Contamination must be filled out before returning to the factory, and downloaded from the Leybold website, filled out, and attached to the packaging. Devices without a declaration will be returned or incur additional cleaning fees.

Maintenance cycle and spare parts recommendations

Calibration cycle: It is recommended to perform zero point (ATM and HV) adjustment once a year.

Cleaning: If measuring gases containing dust, it is necessary to regularly clean the sensor inlet; You can use a soft brush or compressed air.

Spare parts: It is recommended to stock 1-2 sensors (please consult Leybold for part numbers) for quick replacement.

Repair: Any internal repairs (except for sensor replacement) must be carried out by authorized Leybold personnel, otherwise the warranty will be invalidated.

Precautions for replacing old models

If you are using an old THERMOVAC (such as TTR 91, TTR 96, etc.) or other brand vacuum gauge, please note when replacing it with TTR 101:

Output characteristics: TTR 101 outputs logarithmic signals ranging from 0 to 10.23 V, with a pressure voltage relationship of 1.286 V/decade. The old model may output 0~10 V linearly or with different slopes, and the calibration curve needs to be reconfigured in the controller.

Switching logic: default low point trigger (closed when pressure is below threshold), old systems may use high point trigger. PLC logic can be changed or modified through Profibus or on-site programming.

Identification resistor: TTR 101 provides a 71.5 k Ω identification resistor for the controller to automatically identify the range. Ensure that the controller supports reading the resistor.

Flange size: TTR 101 standard is DN 16 ISO-KF. If the old system uses DN 25 KF or other specifications, an adapter or flange replacement is required.

Profibus integration: The TTR 101 PB requires a GSD file, which can be downloaded from the Leybold website. The node address is set through a dip switch (MSD/LSD) rather than software.