The Teledyne Hastings Instruments Digital AVC (DAVC) is a digital readout vacuum gauge designed for precise measurement in various vacuum systems. It is compatible with three popular gauge tube families: DV-4, DV-5, and DV-6, offering a wide range of pressure measurement capabilities.
Function Description:
The DAVC operates by amplifying an analog, non-linear signal from a heated gauge tube, converting it into a 0-1 volt signal. A precision A/D converter and microprocessor then measure this signal, convert it to a pressure reading based on the gauge tube's output/pressure function, and provide the result via a serial communications port. Additionally, the device offers a user-selectable linear analog output. The DAVC is designed for use with rugged, noble-metal thermocouple (TC) gauge tubes, ensuring long life and minimal maintenance. It also features two open collector circuits for pressure alarms, allowing for over-pressure and under-pressure condition signaling. The device can be configured to report pressure in Torr, mbar, or Pascal, with the option to change units via the RS-232 serial interface.
Important Technical Specifications:
- Input Power: 11-32 VDC, 0.7 Watts
- Cable: Combination power and RS232 cable, 1.5 meters included. For CE Compliance, cable should not exceed 3.0 meters.
- Weight (Approx.): 0.27 lbs (123 Grams) W/O Tube & Cable
- Height (Length): 2.8", W/O Tube & Cable
- Width / Depth: 1.75"
- Operating Temperature Range: -20°C to 70°C
- Standard Metal Gauge Tube: DV-6R, DV-5M, DV-4R.
- Overpressure (Gauge tubes): 50 psig max.
- Material of Construction: DAVC Housing: Aluminum; Thermocouple: Glass, Noble Metal.
- Connections: High Density, 15-Pin, D Connector; Octal Tube Socket for Thermocouple.
- Alarms: 0.50 Amps max.
- Tube Leak Test: <1x10⁻⁴ atm cc/sec He.
- Accuracy:
- DV4: 0.02 – 20 Torr, ± (20% of Reading + 0.01 Torr)
- DV5: 0.1 – 100 mTorr, ± (20% of Reading + 0.2 mTorr)
- DV6: 0.001 – 1.0 Torr, ± (15% of Reading + 0.001 mTorr)
- Non-Linear Analog Output: 0-1 VDC
- Linear Analog Output: 0-1, 0-5, 0-10 VDC, and 0-20mA, 4-20mA
- Digital Output: RS232 (9600 / 19.2k baud) (6-pin modular connector)
- AC Tube Drive: 0.3 – 0.4 VAC, true RMS, 1 kHz square wave (Compatible with DV-4, DV-5, and DV-6 tubes)
- Tube Input: 0 – 10 mVDC, (compatible with DV-4, DV-5, and DV-6 tubes)
- Single Set Point Output: Open-collector transistor for over set point.
- Gauge Tube Ranges:
- DV-6: 1.0 - 1000 mTorr
- DV-5: 0.1 – 100 mTorr
- DV-4: 0.2 – 20 Torr
- CE Standard Compliance: EN61010 (Safety), EN61326 (EMC/EMI Family), EN55011 (Conducted/Radiated), EN61000-4-2 (ESD), EN61000-4-3 (RF), EN61000-4-6 (Conducted Immunity).
Usage Features:
- Quick Start: Installation involves connecting the appropriate gauge tube, power supply (11-32 VDC), and setting the atmosphere tube output using the ATM button. The ATM button, when pressed, sets the atmosphere tube output for the individual tube, with LEDs flashing to indicate activity. Holding the button longer than 3 seconds resets the adjustment to default.
- Pressure Unit Selection: The DAVC can be configured for Torr, Pascal, or mbar. While factory-etched on the housing, units can be changed via the RS-232 serial interface using commands like U1 (Torr), U2 (Pascal), or U3 (mbar).
- Analog Output: A non-linear analog signal output (pin 7, yellow) provides 0-1 VDC, corresponding to the selected tube's output range. This signal is measured against the Analog Signal Common line (pin 6, violet). The voltage signal can be mapped to a pressure value using a specific equation provided in the manual. Linear analog outputs (0-1V, 0-5V, 0-10V, 0-20mA, 4-20mA) are also available, with the specific range selected via serial commands.
- Pressure Alarms: Two open collector circuits provide alarm signals. Alarm 1 (gray wire, pin 1) indicates an over-pressure condition, and Alarm 2 (brown wire, pin 2) indicates an under-pressure condition. These circuits require external power and current-limiting resistance from the user. The maximum continuous current should not exceed 0.5 amps to prevent damage.
- Digital Communications: RS-232 communication is supported at 9600 or 19200 baud, 8 data bits, 1 stop bit, no parity, and no handshaking. Commands are sent with a carriage return () terminator. The device supports various commands for querying device ID, current pressure, set point, sensor type, user data, software version, and DAC values.
- Parameter Modification: Users can modify various parameters via serial commands, including selecting linear output ranges (0-20mA, 1V, 4-20mA, 5V, 10V), enabling/disabling data streaming, enabling/disabling the set-point potentiometer, modifying set points, and adjusting DAC zero and span values.
- Calibration: The DAVC allows for calibration of the high end (at atmosphere) and low end (using a known vacuum or a reference tube). The ATM button is used for high-end adjustment. The HTR potentiometer on the top panel is used for low-end adjustment, either by achieving a known vacuum or by connecting a THI reference tube (DB-16D for DV-4, DB-18 for DV-5, DB-20 for DV-6).
Maintenance Features:
- Gauge Tube Contamination: Gauge tubes are shipped with a protective cap to prevent contamination. If a gauge tube produces significantly higher pressure readings than a reference tube, it may indicate contamination. Cleaning can be attempted internally with high-purity isopropyl alcohol.
- Software Reset: A software reset command (/) is available to reset the instrument without overwriting parameters saved in non-volatile memory.
- Autobaud: The device can automatically match the baud rate of the terminal by sending . The baud rate is then stored in EEPROM for future power-ups.
- Warranty: Teledyne Hastings Instruments provides a one-year warranty against defects in material and workmanship. Defective instruments should be returned with a Return Material Authorization (RMA) number. Non-warranty repairs also require an RMA and a written description of the problem, with a minimum charge for processing and inspection if the user chooses not to proceed with repairs.
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