THERMOVAC MEMS Vacuum Gauge Guide

Extract the system to<5 × 10 ⁻⁵ mbar and hold for at least 2 minutes.

Use the accompanying adjustment tool (needle) to press the "ADJ" button (if available), or send adjustment commands through the digital interface.

The transmitter sets the current pressure to zero (5 × 10 ⁻⁵ mbar).

After restoring atmospheric pressure, atmospheric pressure adjustment can be performed (if this function is available).

Note: For models without buttons (such as TTR 91 N), zero adjustment needs to be completed through a controller or digital interface.

Gas type dependence

The MEMS Pirani sensor is based on thermal conductivity, so the relationship between the indicated pressure and the actual pressure depends on the thermal conductivity of the gas. The reading deviation of different gases within the range of 1 × 10 ⁻ ³~100 mbar can be converted by a correction factor. Usually, transmitter factory calibration is for nitrogen/air.

Correction factors for common gases (refer to TTR 101 manual):

He, H ₂: 0.8

Ne：1.4

Air, N ₂, O ₂ CO：1.0

Ar, CO ₂: 1.7

Kr、 Water vapor: 2.4

Xe、Freon：3.0

For the coating version (C model), the correction factor is basically the same because the coating thickness is extremely small and does not affect the thermal conductivity characteristics.

Important note: Above 100 mbar, the relationship between thermal conductivity and pressure is no longer linear, and the measurement accuracy significantly decreases (± 25%). For high-precision measurements near atmospheric pressure, a capacitive thin film vacuum gauge should be used.

Set point relay configuration (S model)

TTR 91 SN, TTR 96 N, TTR 911 SN, and TTR 916 N provide 2 or 3 programmable set point relays. Each relay can independently set a threshold and trigger mode (low point trigger or high point trigger).

7.1 Setting method

Using the buttons (TTR 91 SN/96 N): Similar to the operation of TTR 101, press the SP1/SP2 button to enter the setting mode and adjust the threshold with a needle.

Through the display screen (TTR 911 N/916 N): touch screen operation, intuitively set thresholds and hysteresis.

Through the digital interface (TTR 911 SN/CN): write parameters via RS 232, EtherCAT, or Profibus.

7.2 Delay

The default hysteresis is 10% of the threshold. For example, if a low point trigger is set (the relay closes when the pressure is below the threshold), with a threshold of 1 × 10 ⁻ ² mbar, the relay closes when the pressure drops to 1 × 10 ⁻ ² mbar and opens when the pressure rises to 1.1 × 10 ⁻ ² mbar to avoid shaking.

7.3 Contact Capacity and Lifespan

Rated load: 1 A @ 30 V AC/DC resistive

Minimum load: 10 mA @ 5 V (recommended for low-level signals)

Lifespan: 100000 cycles under 1A load; 2000000 cycles under 0.2 A load

Attention: The relay is a solid-state type with no mechanical contacts, but still has a conducting resistance (≤ 100 m Ω). Not suitable for inductive loads (such as solenoid valves), an external intermediate relay is required.

Digital interface and fieldbus

8.1 RS 232（TTR 911 SN）

Interface type: RS 232, 3-wire (Tx, Rx, GND)

Baud rate: configurable (usually 9600 or 19200)

Function: Read pressure value, read/write set point, zero/atmospheric pressure adjustment, diagnosis

Applicable scenario: point-to-point communication with PC or old PLC

8.2 EtherCAT（TTR 911 CN）

Compliant with IEC 61158 Type 3 standard

Integrated into industrial Ethernet networks with high real-time performance

Support CoE (CANopen over EtherCAT) protocol

Need GSD file (can be downloaded from Leybold website)

8.3 Profibus（TTR 911 CN）

Profibus DP slave station

The node address can be set through hardware dip switches or software settings

Automatic transmission rate detection

Provide GSD files

Note: Profibus and EtherCAT versions do not provide display screens, all parameters are set through the bus.

Troubleshooting and Maintenance

9.1 Common Fault Phenomena and Countermeasures

Possible causes and solutions for the phenomenon

No analog output, LED ring not lit, power supply missing or polarity reversed. Check for 9-30 V DC power supply and confirm positive and negative poles

Output signal constant 0 V (<0.5 V) sensor malfunction or connection problem check cable; Replace the sensor (see 9.2)

Abnormal high or low zero drift of output signal; The gas type has not been corrected and zero point adjustment has been performed; Apply gas correction factor

LED ring red flashing sensor error, power off and restart; If it still exists, replace the sensor

The relay does not operate and the set point is not set correctly; The pressure has not reached the threshold check set value; Confirm trigger direction (low/high)

Digital communication failure, cable disconnection; Baud rate mismatch; Node address conflict check for physical connections; Confirm communication parameters; Replace GSD file

The reading fluctuates greatly, and there is airflow impact at the installation location; Installing electromagnetic interference barriers; Check the shielding grounding

9.2 Sensor replacement

Models such as TTR 916 N and TTR 911 CN offer replaceable sensors (part numbers 230650V02 or 230651V02). Replacement steps:

Remove the transmitter from the vacuum system and release it to atmospheric pressure.