TELEVAC MX7M User manual

MX7M Cold Cathode Ionization Gauge
Instruction Manual
The Fredericks Company - Televac
2400 Philmont Avenue
Huntingdon Valley, PA 19006
email: [e-mail]
tel: [phone]
fax: [phone]

Instruction Manual MX7M Active Gauge
Contents
1 Introduction................................................... 2
1.1 Disclaimer................................................. 2
1.2 Description ................................................ 2
1.3 OperatingSpecifications ....................................... 2
1.4 Dimensions................................................ 3
1.5 SafetyInformation ........................................... 4
1.6 QuickStartGuide............................................ 5
2 Setup ....................................................... 5
2.1 Installation ................................................ 5
2.2 ElectricalInformation ......................................... 5
2.3 Turning the High Voltage On and Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4 MenuNavigation ............................................ 7
2.5 MenuStructure ............................................. 7
2.6 Explanation of Menu Items and Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.7 AnalogOutput .............................................. 12
2.8 CleaningtheMX7MSensor...................................... 15
3 RS-485andUSBCommunications..................................... 17
3.1 Changing Communications Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2 CommunicationsSpecifications................................... 17
3.3 RS-485andUSBCommandList................................... 18
3.4 RS-485SampleCommands ..................................... 21
3.5 USBSampleCommands........................................ 22
3.6 RS-485 and USB Communications Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.7 FirmwareUpdates............................................ 23
List of Tables
1 OperatingSpecifications .......................................... 2
2 GasConversionFactors........................................... 10
3 Replacement Component Part Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4 RS-485 Communication Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5 USBCommunicationSpecifications ................................... 17
6 RS-485 and USB General Read Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7 RS-485 and USB General Write Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8 RS-485 and USB Set Point Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9 USB Commands for Setting RS-485 Communications Settings . . . . . . . . . . . . . . . . . . 20
10 RS-485CommandExamples........................................ 21
11 USBCommandExamples.......................................... 22
12 RS-485 and USB Communications Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
13 RS-485andUSBStatusCommands ................................... 23
List of Figures
1 MX7MDimensionalDrawing........................................ 3
2 MX7M Electrical Connection Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Graph of MX7M Sample Analog Output Functions . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4 Cross-sectional Diagram of the 7M Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
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Instruction Manual MX7M Active Gauge
1 Introduction
1.1 Disclaimer
All information in this manual is subject to change without notice. The Fredericks Company assumes
no responsibility for inaccuracies in product specifications or any liability arising from product use.
Please contact Televac at [e-mail] or call [phone] with comments or
questions.
1.2 Description
The MX7M is cold cathode ionization gauge with a measurement range of 5×10−11 Torr to 1×10−2Torr.
It utilizes a Televac cold cathode ionization sensor in the inverted magnetron configuration with part
numbers 2-2183-KF25 (KF25 flange version), 2-2183-KF40 (KF40 flange version), 2-2183-KF16 (KF16
flange version) or 2-2183-CF40 (CF40 flange version). It has a two color OLED display with selectable
units of Torr, Millibar, and Kilopascal. Settings can be changed through RS-485 communications with
a PC, through USB communications with a PC, or through the unit’s front panel using four capacitive
touch buttons located on the top of the unit. The MX7M has two set points, one relay and one open
collector, and a selectable analog output option. The analog output is a configurable 0-10 V output
that includes options for linear, linear-by-decade, and logarithmic formats.
1.3 Operating Specifications
Table 1: Operating Specifications
Operating Range 5×10−11 to 1×10−2Torr
Communications RS-485 and USB
Programmable Set Points 2
Set Point 1 Open Collector
Set Point 2 Relay
Analog Output Configurable 0 to 10 V
Supply Voltage +22 to +26 V DC
Maximum Power 8 W
Calibration Medium Dry air or nitrogen
Overpressure 150 PSI
Digital Output Resolution 2 significant digits with exponent
Analog Output Resolution 16 bits
Operating Temperature 0◦C to 50◦C
Storage Temperature −20◦C to 60◦C
Bakeout Temperature 250◦C (electronics removed)
Response Time ≤1second
Accuracy
1×10−9Torr to 1×10−3Torr ±30%
Analog Output ±10 mV
Display Readable Distance 3 m (10 feet)
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Instruction Manual MX7M Active Gauge
1.4 Dimensions
Figure 1: MX7M Dimensional Drawing
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Instruction Manual MX7M Active Gauge
1.5 Safety Information
START BY READING THESE IMPORTANT
SAFETY INSTRUCTIONS AND NOTES
In these instructions the word “product” refers to the MX7M and all of its approved parts and acces-
sories. NOTE: These instructions do not and cannot provide for every contingency that may arise in
connection with the installation, operation, or maintenance of this product. Should you require further
assistance, please contact Televac at the email address found in the footer of this manual.
This product has been designed and tested to offer reasonably safe service provided in it is installed,
operated and serviced in strict accordance with these safety instructions.
These safety precautions must be observed during all phases of operation, installation, and service
of this product. Failure to comply with these precautions or with specific warnings elsewhere in this
manual violates safety standards of design, manufacture, and intended use of the instrument. Televac
disclaims all liability for the customer’s failure to comply with these requirements.
 READ Instructions – Read all safety and operating instructions before operating the product.
 RETAIN instructions – Retain the safety and operating instructions for future reference.
 HEED warnings – Adhere to all warnings on the product and in the operating instructions.
 FOLLOW instructions – Follow all operating and maintenance instructions.
 ACCESSORIES – Do not use accessories not recommended in this manual as they may require a
technician to restore the product to its normal operation.
The MX7M has voltages up to 4500 volts. As such, it represents a shock hazard and should be handled
with caution. Any disassembly of the gauge should be carried out by a trained professional and with
the power disconnected.
Do not substitute parts or modify instrument. Because of the danger of introducing addi-
tional hazards, do not install substitute parts or perform any unauthorized modifications
to the product. Return the product to Televac for service and repair to ensure that safety
features are maintained. Do not use this product if it has unauthorized modifications.
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Instruction Manual MX7M Active Gauge
1.6 Quick Start Guide
1.6.1 Check what you’ve received
Compare what you’ve received to your purchase order.
1.6.2 Safety Instructions
Review all safety instructions outlined in Section 2
1.6.3 Connect Power
Connect a 24V power supply to the unit. See the pin out in Figure 2 for more information.
1.6.4 Check the Measurement Screen
The unit should power up and display "OFF" on the measurement screen. Do not attempt to turn on
the high voltage.
1.6.5 Power down the MX7M
Power down the MX7M and install it on a vacuum stand for use.
2 Setup
2.1 Installation
Each MX7M is designed to be used in conjunction with a 7M sensor. The 7M sensor can be mounted
in any position however it is recommended to mount it away from any contaminants that might be
in the system as over time this can affect the measurement accuracy. Mounting the 7M sensor close
to the area where vacuum measurement is desired is preferred to increase the accuracy. Each 7M
sensor has a key that only allows for the MX7M to mate with the sensor in the proper orientation.
Rotate the MX7M until the correct alignment is obtained and the MX7M is able to slide onto the 7M
sensor. Connect the power connector to the top of the unit and be sure to tighten the screws so that
a firm connection is maintained.
Try to avoid connecting the MX7M to the vacuum chamber by long or narrow piping as this may
affect the accuracy and response time of the unit. Avoid mounting the unit near a heater within the
chamber as this may affect the measurement accuracy. Excessive vibration of the unit may affect
accuracy and decrease the life of the unit. Exposure to oils and other contaminants will decrease the
accuracy and decrease the life of the sensor. Do not expose the unit to corrosive gases.
2.2 Electrical Information
Power connectors and adapters for use with the MX7M are available for purchase from Televac. Op-
erators wishing to create their own adapters should refer to the pin out of the MX7M below. Each
connection labeled “Floating” has no connection and should remain so.
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Instruction Manual MX7M Active Gauge
Figure 2: MX7M Electrical Connection Information
Pin Description
1Analog Output (Ground)
2RS-485 A(-)
3SP2 NC
4SP2 NO
5SP1 Open Drain
6Starter Output (5V)
7Starter Output (Ground)
8Supply Voltage
9Analog Output (0-10 V)
10 RS-485 B(+)
11 SP2 Com
12 SP1 Source
13 Sensor Voltage Control
14 Sensor Voltage Control
15 Supply Voltage (Ground)
2.3 Turning the High Voltage On and Off
The MX7M has an operating range that does not include measurement above 1×10−2Torr. If the unit
is operated above 1×10−2Torr, the sensor will be damaged and electrical arcing inside the sensor
may occur. To prevent this, the unit should be paired with a low vacuum gauge, such as the MX4A or
MX2A, to ensure safe operation.
The MX7M provides two control methods for toggling the high voltage; Menu Control and Pin Control.
To select which method is used, navigate to the Vsense Control menu screen and select either Menu
or Pins. Pin Control is provided through pins 13 and 14 of the MX7M connector.
To turn on the sensor when Menu Control is selected, use one of the following two options: from the
Measurement Screen, press SEL to navigate to the Vsense Control, then press ENT to unlock the con-
trol, press UP to toggle the status to ON, and then press ENT to save the change. The high voltage
should now turn on. In Menu Control mode, the high voltage can also be toggled by sending the
appropriate command to turn on the sensor through RS-485 or USB Communications. To turn off the
sensor in Menu Control mode, navigate to the Vsense Control screen, press ENT to unlock the menu,
press UP to toggle the status to OFF, and press ENT to save the change. Alternatively, when in Menu
Control mode, the user may send the appropriate command to turn off the sensor through RS-485 or
USB Communications. See section 3 for more information.
To turn on the sensor when Hardware Control is selected, short pins 13 and 14 together. To turn off
the sensor, open the path between pins 13 and 14. This functionality is included to easily interface
with a low vacuum gauge, such as the Televac MX2A or MX4A, to automatically control the unit via an
open collector or relay. Contact Televac Sales for more information or see Application Note 3022.
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Instruction Manual MX7M Active Gauge
To protect the sensor from damage, if the sensor high voltage is toggled on when in either Menu
Control or Pin Control mode the pressure is above 1×10−2Torr, overcurrent protection will turn the
sensor off. If the sensor is in Menu Control mode, then a command to turn on the sensor will need
to be sent via communication or through the front panel to toggle the high voltage on again. If Pin
Control is enabled, then the unit will attempt every to turn the high voltage on every 60 seconds until
overcurrent protection does not occur.
2.4 Menu Navigation
The MX7M contains many operator customizable features. Changing these features is possible through
the menu or via RS-485 or USB communications. To navigate the menu simply use the buttons found
on top of the MX7M . The four buttons include the SEL button, an UP arrow, a DOWN arrow, and an
ENT button. Using the SEL button allows the operator to change between menu categories. Using the
ENT button allows the user to enable value editing and save values in addition to toggling between
options where appropriate. Using the UP and DOWN arrows allows navigation through menu options.
The UP and DOWN arrow buttons are also used to edit values.
2.5 Menu Structure
1. Measurement Screen
2. High Voltage Toggle
3. System Settings
(a) Units
i. Torr
ii. mbar
iii. kPa
(b) Gas Type
i. Hydrogen
ii. Helium
iii. Neon
iv. Argon
v. Krypton
vi. Carbon Dioxide
(c) Resolution
i. Low Resolution
ii. High Resolution
(d) Vsense Control
i. Menu Control
ii. Pin Control
(e) Diagnostics
i. FW Date
ii. FW Version
4. Calibration
(a) 1×10−6Torr
(b) 1×10−5Torr
(c) 1×10−4Torr
(d) 1×10−3Torr
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Instruction Manual MX7M Active Gauge
(e) Analog Output Adjustment
5. Set Points
(a) SP1 Off
(b) SP1 On
(c) SP2 Off
(d) SP2 On
6. Output
(a) Analog Output
i. Linear
A. 10 V Pressure
B. 0 V Pressure (Non-settable)
ii. Linear by Decade
iii. Linear by Decade 7F
iv. Logarithmic
A. 10 V Pressure
B. 0 V Pressure
(b) RS-485 Output
i. Address
ii. Baud Rate
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Instruction Manual MX7M Active Gauge
2.6 Explanation of Menu Items and Navigation
Below is a general explanation of each level of the MX7M menu structure.
2.6.1 Measurement Screen
The measurement screen contains the reading of the sensor in easy-to-read blue digits and includes
units. In addition to the digital reading, the yellow bar on the measurement screen provides an analog
indication of the pressure based on a logarithmic scale. At 1×10−2Torr the yellow bar should stretch
across the width of the screen. At 5×10−11 Torr the yellow bar will disappear, and at 7×10−7Torr,
the yellow bar will be approximately half way across the screen.
The sensor high voltage must be turned on to display a reading. If the high voltage is not on, the
measurement screen will display "OFF". When the high voltage is toggled on, the unit will display
"Starting" until the unit has reached a steady measurement. Once a steady measurement is obtained,
it will be displayed. If the unit goes into overcurrent protection mode, the display will read "Over". If
Pin Control is enabled, the unit will attempt to start every 60 seconds. If overcurrect protection mode
continues upon an attempted start, the unit will continue to read "Over". If Menu Control is enabled,
the unit will display "OFF" and the high voltage will need to be turned on again. See 2.3 for more
details. If the high voltage is enabled and the pressure is below 5×10−11 Torr, then the unit will
display "Low" to indicate that the pressure is below the measurable limit.
2.6.2 High Voltage Toggle
If the unit is in Menu Control Mode, then the user must turn on the high voltage by sending a command
over communications or by navigating to the High Voltage Toggle menu screen. Once at the High
Voltage Toggle screen, press ENT to unlock the screen, press UP or DOWN to change the setting, and
then press ENT to save the change. The high voltage will then turn on and a pressure indication will
be displayed on the Measurement Screen. If the pressure is too high, the unit will go into overcurrent
protection mode and the high voltage will turn off. To restart the unit once a safe pressure has been
achieved at the gauge, simply repeat the steps to turn on the high voltage.
2.6.3 System Settings
The system settings menu contains the ability to change the measurement units, apply a gas correc-
tion factor, change the digital resolution to display an extra digit, and set the Vsense Control method
for the unit. There is also a diagnostic screen for use by Televac service representatives to trou-
bleshoot the unit.
To modify the system settings:
 Navigate to the measurement screen.
 Press SEL twice.
 Press UP and DOWN arrows to navigate between panes under the system settings heading.
 Press ENT to unlock the specific screen. ADJ will appear at the top of screen to show that the
unit is unlocked and that a change can be made.
 Press UP or DOWN to select between the options available.
 Press ENT to save the changes or SEL to navigate away without saving. ADJ will disappear from
the screen after either ENT or SEL has been pressed.
A.Units
The MX7M has three selectable units to choose from: Torr, mbar, and kPa. When changing units,
all of the relevant settings previously saved in the unit will be converted to the appropriate units.
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Instruction Manual MX7M Active Gauge
B.Gas Type
The MX7M is an indirect pressure sensor and its accuracy will be effected by the presence of
gases other than nitrogen. The MX7M has the ability to apply correction factors for six pre-
defined gases: hydrogen, helium, neon, argon, krypton, and carbon dioxide. These correction
factors have been experimentally determined by Televac to yield the maximum accuracy avail-
able. Conversion factors for use with the MX7M when gases to be measured are other than
Nitrogen are listed. For users wishing to manually apply the conversion, multiply the unit read-
ing by the factor in the table below to convert to the correct pressure reading.
Table 2: Gas Conversion Factors
Gas Type Conversion Factor
Nitrogen 1.00
Hydrogen 2.20
Helium 6.40
Neon 4.10
Argon 0.81
Krypton 0.56
Carbon Dioxide 0.71
C.Resolution
The MX7M displays two significant digits by default (low resolution). The user may choose to
operate the gauge in high resolution mode in which the unit will display three significant digits.
The
D.High Voltage Control
The MX7M has an upper range of 1×10−2Torr and will be damaged by use above this pressure.
Toggling of the unit on and off can be accomplished via software, through the menu or via
communications, or hardware means, via two pins on the DB-15 connector. For more information
on the difference between hardware and software control, see Section 2.3.
E.Diagnostics
The MX7M contains a diagnostic screen for use by Televac service representatives to trou-
bleshoot the unit. The Diagnostic screen contains the FW version of the unit and the date the
software was last revised.
2.6.4 Calibration
To ensure that the unit always displays with the most accuracy, the MX7M includes a number of
operator-configurable calibration points. While the MX7M is factory calibrated, the use of the in-
cluded calibration points may become necessary after extended use, contamination, etc. If accuracy
is critical, it is recommended to return the sensor to Televac for NIST-traceable calibration.
The unit should only be calibrated when under vacuum and a NIST-traceable calibrate reference is
available. Any change of calibration values by the customer voids any Televac calibration and should
only be used in when in line with a defined quality system.
To modify the calibration settings:
 Navigate to the measurement screen.
 Press SEL three times.
 Press the UP and DOWN arrows to navigate between panes under the calibration heading.
 Press ENT to select the calibration point.
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Instruction Manual MX7M Active Gauge
 Press UP or DOWN until the unit matches the reference in use for calibration.
 Press ENT to save the adjustment. Press SEL to exit without saving.
Note 1: Calibration should be performed in the following order: 1×10−6Torr adjustment, 1×10−5
Torr adjustment, 1×10−4Torr adjustment, 1×10−3Torr adjustment. Failing to calibrate in this order
will result in inaccuracies.
Note 2: CHANGING CALIBRATION SETTINGS VOIDS NIST-TRACEABLE CALIBRATIONS!
A.10−6Torr
The 1×10−6calibration point allows the gauge to adjust the pressure reading at 1×10−6Torr.
This calibration point should not be use to adjust the gauge reading below a reference pressure
of 5×10−7Torr or above 2×10−6Torr.
B.10−5Torr
The 1×10−5calibration point allows the gauge to adjust the pressure reading at 1×10−5Torr.
This calibration point should not be use to adjust the gauge reading below a reference pressure
of 5×10−6Torr or above 2×10−5Torr.
C.10−4Torr
The 1×10−4calibration point allows the gauge to adjust the pressure reading at 1×10−4Torr.
This calibration point should not be use to adjust the gauge reading below a reference pressure
of 5×10−5Torr or above 2×10−4Torr.
D.10−3Torr
The 1×10−3calibration point allows the gauge to adjust the pressure reading at 1×10−3Torr.
This calibration point should not be use to adjust the gauge reading below a reference pressure
of 5×10−4Torr or above 2×10−3Torr.
E.Analog Output Adjustment
The MX7M allows for an offset calibration of the MX7M to provide maximum accuracy for users
where long cable lengths are affecting the accuracy. To calibrate the analog output, adjust
the pressure of the vacuum system to a stable pressure corresponding to the a value near the
maximum analog output. Measure the analog output with a volt meter, compare the displayed
pressure on the gauge to the calculated pressure based on the analog output, and adjust the
calibration until the displayed pressure and calculated pressure match. See section 2.7
2.6.5 Set Points
The MX7M contains two set points for the convenience of the operator. Set point 1 is an N-Channel
60 V MOSFET open collector. It has a maximum current rating of 1 A. The data sheet can be found at
www.vishay.com/docs/69958/si2308bds.pdf. Set point 2 is a relay with a maximum switching voltage
of 220 V DC (250 V AC) and a maximum switching current of 2 A. The data sheet can be found at
www.te.com/catalog/pn/en/1393788-3.
To modify the set point settings:
 Navigate to the measurement screen.
 Press SEL four times.
 The set point screen contains set point 1 off.
 To access set point 1 on, set point 2 off, or set point 2 on, press DOWN from the initial set point
screen.
 When the correct set point is selected, press ENT to unlock the set point adjustment screen.
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Instruction Manual MX7M Active Gauge
 Press UP and DOWN to change the value.
 When the desired reading is reached, press ENT to save the change or SEL to navigate away
without saving the change.
2.6.6 Output
The MX7M provides a user selectable analog output as well as RS-485 and USB digital outputs.
To modify the output settings:
 Navigate to the measurement screen.
 Press SEL five times.
 Press UP and DOWN to navigate between the analog output and RS-485 screens.
 When the desired field is present, press ENT to enter the heading.
 To change the desired setting, press ENT to unlock the setting.
 Press UP or DOWN to adjust the setting.
 Press ENT to save the setting or SEL to navigate away without saving.
A.Analog Output
The types of analog output are listed below. For more information on the types of output, please
see Section 2.7.
(a) Linear
i. 10V
ii. 0V (non-settable)
(b) Linear by Decade
(c) Linear by Decade 7F
(d) Logarithmic
i. 10V
ii. 0V
B.RS-485 Output
The RS-485 settable fields are listed below. Please see the Section 3 for more details and a
complete list of commands. Listed below are the fields within the RS-485 Output screen.
(a) Address
(b) Baud Rate
2.7 Analog Output
The MX7M provides the option for outputting the pressure reading in an analog form. Operators who
wish to use PLCs to monitor processes should find this function useful. There are four different analog
output formats to choose between. The formats include Logarithmic, Linear by Decade, Linear by
Decade 7F, and Linear.
A.Linear
The Linear output covers a select range of the MX7M with a linear scale. The 10 Volt or full-scale
value of the output can be selected from the following values: 1×10−5Torr, 1×10−4Torr, or
1×10−3Torr. The scale extends three decades below the full-scale value. Three decades below
the 10 V value is the 0 V value. This corresponds to the low end of the range and output below
the 0 V value is not available. For a wider range use a different analog output formate. Note
that only the 10 V exponent is selectable. When navigating through the menu, the 0 V exponent
will be viewable but not settable. Use the high value (1.0×10H)exponent H in the following
equation to convert the voltage output to pressure:
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Instruction Manual MX7M Active Gauge
Votge Otpt ×10H−1=Pressre
To select the Linear output, navigate to the Analog Output screen, press ENT, and then use the
UP or DOWN arrow to select Linear. Press ENT to save the change. Then press DOWN once to
navigate to the Output High screen. Press ENT to unlock the screen and press UP or DOWN to
select the full scale pressure for the analog output.
B.Linear by Decade
The Linear by Decade output spans the MX7M measurement range. It uses the units digit of
the voltage reading to communicate the decade of the pressure reading and the units after
the decimal to communicate the specific pressure using the very generalized expression below,
where A, B, C, and D are digits ranging from 0-9:
Votge =A.BCD →Pressre(Torr) = 10A−11 ×.BCD
For example, a voltage reading of 8.367 Volts corresponds to a pressure of 3.67 ×10−4Torr.
108−11 ×.367 =10−3∗.367 =3.67 ×10−4Torr
To select the Linear by Decade output, navigate to the Analog Output screen, press ENT, and
then use the UP or DOWN arrow to select Linear by Decade. Press ENT to save the change. Note
that this analog output extends from 0 V to 9.1 V.
C.Linear by Decade 7F
The Linear by Decade 7F output spans the MX7M measurement range and is included for in-
creased compatibility of the MX7M to serve as a drop-in replacement for previous Televac offer-
ings. It uses the units digit of the voltage reading to communicate the decade of the pressure
reading and the units after the decimal to communicate the specific pressure using the very
generalized expression below, where A, B, C, and D are digits ranging from 0-9:
Votge =A.BCD →Pressre(Torr) = 10A−10 ×.BCD
For example, a voltage reading of 8.367 Volts corresponds to a pressure of 3.67 ×10−3Torr.
108−10 ×.367 =10−2∗.367 =3.67 ×10−3Torr
To select the Linear by Decade output, navigate to the Analog Output screen, press ENT, and
then use the UP or DOWN arrow to select Linear by Decade 7F. Press ENT to save the change.
D.Logarithmic
The Logarithmic output is an accurate output that can cover the entire range of the MX7M
or be used with a selected range. To use this output, the user must select an exponent that
corresponds to 10 V and the exponent that corresponds to 0 V. The exponent chosen for this
format uses the formula below to convert the output voltage into a pressure measurement. Note
that H is the exponent of the 10 V value and L is the exponent of the 0 V value. Volt is the analog
output voltage.
Spn =10
H−L
Oƒ ƒ set =0−L
Pressre (Torr) = 10Vot
Spn −Oƒ ƒ set
For example, with the logarithmic range set to a 0 V value of 1×10−7and a 10 V value of 1×10−3
and a voltage reading of 3.075 Volts, the pressure corresponds to:
Spn =10
−3−(−7)=2.5
Oƒ ƒ set =0−(−7) = 7
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Instruction Manual MX7M Active Gauge
Pressre (Torr) = 10 3.075
2.5−7=1.7×10−6Torr
To select the Logarithmic output, navigate to the Analog Output screen, press ENT, and then use
the UP or DOWN arrow to select Logarithmic option. Press ENT to save the change. Press the
DOWN arrow to navigate to the 10 V exponent selection screen. Press ENT to unlock and then
the UP or DOWN arrow to select the value. Press ENT to save the value. Press the DOWN arrow
to navigate to the 0 V exponent selection screen. Press ENT to unlock the screen and the UP or
DOWN arrow to select the 0 V value.
Figure 3: Graph of MX7M Sample Analog Output Functions
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Instruction Manual MX7M Active Gauge
2.8 Cleaning the MX7M Sensor
Refer to Figure 4 while cleaning the 7M sensor. Before disassembling the sensor, ensure that the unit
is removed from any power source and is removed from the vacuum system. Also ensure that you
have a new copper gasket or a o-ring. See the parts listed below. The cleaning steps are as follows:
1. Remove the sensor from the electronics assembly by loosening the two set screws in the base
of the electronics. A .050” Allen wrench is necessary for this step.
2. Remove the six bolts from the top of the unit. These require a 7/64 Allen wrench.
3. The MX7M ships by default with a copper gasket to allow customers to use the full range of the
MX7M . Any standard CF16 gasket will work with the MX7M . Once the bolts are removed, the
used copper gasket can be pulled free and discarded. Be sure not to scratch the knife-edge
surface.
4. If the gasket has been replaced with an o-ring, handle the o-ring gently and wash with isopropyl
alcohol, methanol, or DI water. Wipe with a lint-free cloth.
5. Visually inspect the o-ring for cracks or tears. If any physical defects are found, the o-ring should
be replaced.
6. Wipe the inside of the tube with scotch-brite or similar. Do not use steel wool due to the magnets
present in the sensor.
7. If wiping the inside of the tube does not remove all build up, bead blast the vacuum wetted
portions of the anode assembly at 30 PSI using 70 to 140 mesh glass beads (labeled with red
and blue in the diagram). Be careful not to damage the knife edge of the sensor.
8. Blast the vacuum wetted portions of the body with glass beads (labeled with blue in the diagram),
concentrating on the pole piece and “O” ring areas, but making sure to clean all surfaces wetted
to vacuum. If the threaded end of the tube needs to be cleaned, it can be bead blasted as well.
9. After cleaning, use compressed dry nitrogen to remove any residual glass beads or dust from
the sensor.
10. Wipe the anode with scotch-brite or similar. Blow with compressed dry nitrogen.
11. Install a new gasket or cleaned o-ring and seat the anode.
12. Before replacing the bolts, observe the keyway locations line up between the anode and the
body.
13. Replace bolts and tighten.
14. Insert sensor into the electronics and tighten the set screws.
15. Reinstall the sensor on the vacuum chamber.
16. Allow several hours for the sensor to degas when your system is pumped down to high vacuum.
17. If properly cleaned and assembled, the sensor is ready for use without re-calibration unless NIST
traceable calibration is required.
Table 3: Replacement Component Part Numbers
Description Part Number
MX7M replacement anode assembly 1-7900-011
DN16 copper gasket 6-4200-031
DN16 viton o-ring 6-4200-030
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Instruction Manual MX7M Active Gauge
Figure 4: Cross-sectional Diagram of the 7M Sensor
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Instruction Manual MX7M Active Gauge
3 RS-485 and USB Communications
This gauge communicates with the host computer through an RS-485 or USB interface. Each commu-
nication correspondence consists of a command line sent by the host computer and a response from
the gauge.
To communicate with the MX7M via RS-485, the user must have an RS-485 capable device to send
commands to the MX7M . Each command must be preceded by a *, the address, and will be an S, R,
W, RC, or WC.
To communicate with the MX7M via USB, the user must have a USB capable device to send commands
to the MX7M . Each command must be preceded by a * and will be an S, R, W, RC, or WC. Because USB
is a serial bus, the unit address is omitted from commands. See the Communications Specifications
heading for information on what settings are necessary to properly communicate with the MX7M .
3.1 Changing Communications Settings
The communication parameters, (baud rate, address, etc.), are changed through the local menu.
Please see the section in this manual entitled Explanation of Menu Items and Navigation for more
information on navigating and editing within the menu. Below are provided some specifics on the
RS-485 and USB Communications of the MX7M .
3.2 Communications Specifications
Table 4: RS-485 Communication Specifications
Interface RS-485 compatible
Data Transfer Method Synchronous/half duplicate method
Baud Rate 9600/19200/38400/57600/115200
Data Format 1 start bit, 8 data bits, 0 parity bits, 1 stop bit
Error Detection Parity bit
Parity Bit None
Stop Bit 1
Transfer Distance Max 100 meters
Table 5: USB Communication Specifications
Interface USB type B receptacle on module
Type USB 2.0
Class USB communications device class (USB CDC)
Baud Rate 115200
Transfer Distance Max 5 meters
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Instruction Manual MX7M Active Gauge
3.3 RS-485 and USB Command List
Table 6: RS-485 and USB General Read Commands
Command Response Description
R1 xx Read units, where xx is:
PA = Pa
TR = Torr
MB = mbar
R3 xx Read resolution, where xx is:
LO = low
HI = high
R5 xyzzabb Read analog output range, where:
x = 1 (linear), 2 (log), 3 (linear-by-decade),
4 (linear-by-decade 7F)
y = high value exponent sign
zz = high value exponent
a = low value exponent sign
bb = low value exponent
R6 xx Read gas type, where xx is:
N2 = Nitrogen
AR = Argon
H2 = Hydrogen
HE = Helium
NE = Neon
KR = Krypton
C2 = Carbon Dioxide
R7Y ppseePPSEE Read SPL (ppsee) and SP2H (PPSEE) settings
Y =1 (Open Collector)
Y =2 (Relay)
R8 x Read sensor voltage control, where x is:
1 = menu control
2 = pin control
R10 x Read high voltage state, where x is:
0 = off
1 = on
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Instruction Manual MX7M Active Gauge
Table 7: RS-485 and USB General Write Commands
Command Response Description
W1xx xx Set units, where xx is:
PA = Pa
TR = Torr
MB = mbar
W3 xx Toggle resolution, where xx is:
LO = low
HI = high
W51yzz 1yzz Set analog output format to linear, yzz = high value
y = high value exponent sign
zz = high value exponent
W52yzzabb 2yzzabb Set analog output format to logarithmic
yzz = high value, abb = low value
y = high value exponent sign
zz = high value exponent
a = low value exponent sign
bb = low value exponent
W53 3 Set analog output format to linear-by-decade
W6xx xx Set gas type, where xx is:
N2 = Nitrogen
AR = Argon
H2 = Hydrogen
HE = Helium
NE = Neon
KR = Krypton
C2 = Carbon Dioxide
Response is new gas type.
W7YppsePPSE ppseePPSEE Set thresholds for set point Y, where:
ppsee = SPL
PPSEE = SPH
Response is new threshold settings for SPL (ppsee) and SPH
(PPSEE).
Y = 1 (Open Collector)
Y = 2 (Relay)
W8x x Set sensor voltage control, where x is:
1 = menu control
2 = pin control
W10x x Set high voltage state, where x is:
0 = off
1 = on
Response is new high voltage setting.
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