Layout
Field Wiring
Block Diagram
Specifications
Operation
Programming and Calibration
Modbus Functions and Register List
The VP-TX-120-SS is the inexpensive alternative to gas detection and environment monitoring. The combination of analog 4-20 mA output and the RS-485 digital port makes this unit the ideal choice to connect to analog controllers and digital PLC's. The choice of Solid State Gas Sensor provides accurate level readings with a life span of up to 7 years under normal applications.
The on board temperature sensor and %RH (Humidity) sensor can be read directly from the RS-485 port or with the LCD display which is internally mounted. The user interface consists of a Status LED, LCD and three pushbuttons. The Status LED indicates OK, LOW, MID, HIGH Alarm. The three pushbuttons and internal LCD provide a convenient calibration method. There are NO potentiometers, all programming and calibration is performed digitally from the user interface. The compact ABS enclosure is rated for IP66 of IEC 529 and NEMA 1,2,4,4x,12 and 13. The interior is EMI/RFI shielded with a nickel conductive coating. For installation convenience, the VP-TX-120-CO comes complete with mounting hardware already installed.
Standard Features
Pre-Programmed Default Sensors and Settings
Figaro Sensor | Gas Type | Gas Name | Gas Range | Units | Calibration Gas | Low Alarm | Mid Alarm | High Alarm |
---|---|---|---|---|---|---|---|---|
TGS826 | NH3 | Ammonia | 0 - 300 | PPM | 300 | 100 | 200 | 300 |
TGS832 | R-134a | Freon | 0 - 3000 | PPM | 1000 | 1000 | 2000 | 3000 |
TGS822 | CO | Carbon Monoxide | 0 - 400 | PPM | 100 | 35 | 50 | 100 |
TGS822 | ALC | Ethanol | 0 - 5000 | PPM | 1000 | 1000 | 2000 | 3000 |
TGS813 | CH4 | Methane | 0 - 50 | %LEL | 20 | 20 | 30 | 40 |
TGS813 | C3H8 | Propane | 0 - 50 | %LEL | 20 | 20 | 30 | 40 |
The VP-TX-120-SS has two printed circuit card assemblies:
1. The main pcb has the LCD, User Interface components, relay. RS485 Rj45 jacks, and the field wiring terminal blocks. This module is common to all the various sensor types.
2. The sensor module is mounted on the door for the enclosure and has the gas sensor, temperature sensor, humidity sensor, pwoer and status LEDs.
Item | Metric | Value |
---|---|---|
I/O | Part Name : | VP-TX-120 Solid State Sensor Transmitter |
Part Number : | VPE-1971 | |
Input : | Figaro Series TGS Solid State Sensor | |
Sensor Heater Voltage : | 5 VDC, +/- 0.1 VDC | |
Resolution : | 4096 AD Counts (12 bit) | |
Accuracy : | +/- 5% up to 100% of Full Scale for GAS Long Term Drift | |
Repeatability : | +/- 5% of Full Scale | |
Linearity : | +/- 10% of Full Scale | |
Internal Temperature Sensor : | 10K Ω NTC 3380 Beta Thermistor | |
Internal Humidity Sensor : | Honeywell HIH-5030 Series, Range 0 to 95% Non-Condensing | |
Sample Rate : | 500 ms Default | |
Warm Up Time : | 5 Minutes for full operation at 25 °C 24 Hours for full specification at 25 °C | |
Relay Output | Qty : | 1 SPDT |
Rating | 2 A | |
Communication | Protocol : | Modbus RTU RS485 |
Baud Rate | Programmable 9600,19200 (N81) | |
Modbus ID | Programmable 1 to 253 | |
Termination | Jumper Selectable Enable or Disable 120 Ohm | |
Wiring | 1 RJ45 Jack, 1 sets of terminal blocks (+V, Data A, Data B, Common) | |
Analog | Output : | 4 - 20 mA |
Drive (Max) | 1000 Ω at 24 VDC Input Field Power | |
Scale | Gas Range (See Above Chart) | |
User Interface | Pushbuttons : | UP. DOWN, ENTER |
Status LEDs - Main Module | Three Alarm Leds, OK, Low, High | |
Program LEDs - Main Module | Three Program LEDs: PGR, SPAN, ZERO | |
Power ON LED - Main Module | Blue, Always On | |
Status LED - Sensor Module | OK, Low, Mid, High, Fault | |
Power ON LED - Sensor Module | Blue, Always On | |
LCD | 2 Line x 8 Character (Mounted on Printed Circuit Board Assembly) | |
Audible | Key Click and High Alarm (Programmable ON or OFF) | |
Processor | Processor : | Microchip PIC18F Series |
Field Connections | Terminal Qty : | 12 |
Method : | Screw, Rising Cage Clamp | |
Torque : | 0.753 N-m (4.3 Lb-in) | |
Screw : | M3 | |
Voltage Rating : | 300 VAC | |
Current Rating : | 15 A | |
Withstanding Voltage : | 1.6 KV | |
Cross section solid conductor AWG min : | 28 | |
Cross section solid conductor AWG max : | 12 | |
Cross section stranded conductor AWG min : | 28 | |
Cross section stranded conductor AWG max : | 12 | |
Stripping Length : | 6-7 mm | |
Physical | Height: | 5.11" |
Width : | 3.93" | |
Depth : | 2.75" | |
Weight : | 200 g | |
Material : | ABS, c/w Stainless Steel Wall Mounting Brackets | |
Weight, Shipping (Qty. 1) : | 300 g | |
Electrical | Power Input Voltage Range (Typical : | 24 VDC |
Power Input (Minimum) : | 9 VDC | |
Power Input (Maximum) : | 28 VDC | |
Current max : | 100 mA | |
Current typical : | 75 mA | |
Ambient | Operating Temperature : | -20 to +65 °C |
Storage Temperature : | -40 to +85 °C | |
Operating Relative Humidity (non-condensing) : | 0 to +95 %RH | |
Storage Relative Humidity (non-condensing) : | 0 to +95 %RH | |
Protection : | IP20 | |
Warranty (Exluding Sensors) | Limited Liability : | Product Replacement 1 Year |
Download : | Warranty Statement |
Getting Started
Connect the VP-TX-120-SS Sensor Transmitter as follows:
4 - 20 mA Output
+V (24 VDC) to TB1, mA Signal Output to TB 2, Common to TB 3.
RS485 (Modbus RTU Protocol)
Data A to TB 8,11 Data B to TB 9 12, Common to TB 7, 10
NOTE: The Analog Output and RS485 are independent of each other and can be used at the same time.
For RS485 operation, the RJ45 Jack can also be used, the pinout is shown in the block diagram above.
Relay Output
NO TB 5 and 6, NC TB 5 and 4
Power On : There is a 120 Second Power On Timer to allow the sensor to stabilize. If the sensor is cold, the sensor should be
allowed to stabilize for a minimum of 24 hours before performing any calibration. During the 120 Second Power On cycle, the LCD will display:
There are 6 Main Display Screens. The different screens are accessed with the UP or DOWN Pushbuttons
Pushbutton Operation : There are three pushbuttons, UP, ENTER and DOWN. The basic operation is UP or DOWN to select the display, ENTER to start or exit a function.
Back to TopNormal Operation LCD Screens Examples shown are for a NH3 (Ammonia) Sensor
Note: During normal operation or programming operation, if a push button is not activated within 120 seconds, the lcd returns to the default display as shown above in point 1.
Back to TopPassword Entry
NOTE: To enter a value, each digit is individually programmed by using the UP or DOWN buttons to select a value. Once the desired digit is programmed, press the ENTER Key to select the next digit. After the final digit is programmed, press the ENTER key to accept the programming. (This method is typical for most programming functions.)
Zero Calibration
NOTE: Before entering the zero calibration, flow 0 gas or fresh air on the sensor to ensure a proper zero gas calibration as soon as the enter button is pressed, the zero cal value will be set
The value should change to 0, if it still drifts, the UP or DOWN push buttons can be used to tweak the value to 0. Press the ENTER button to exit. Each re-entry into the Zero calibration Display Menu resets the Zero Calibration Point.
Zero Calibration is Complete
Span Calibration
The calibration gas value is used to calibrate the sensor. If the user has access to a different calibration gas concentration than the one shown on the display, press ENTER to set the new Calibration Gas Value.
NOTE: The user should apply the calibration gas to the sensor for an appropriate time (minimum 2 minutes) to allow the sensor to stabilize to the calibration gas value before entering the span calibration
Use the UP and DOWN push buttons to make the reading equal to the Span Calibration Gas applied. Please allow four reading updates (4 seconds) in between each button press. There is a software algorithm used where the further away the current reading is from the Cal Gas Value, the higher the adjustment value. The closer the reading is to the Cal Gas Value, the smaller the adjustment. This makes the calibration procedure very efficient.
If there is not enough signal present and a calibration is attempted, the display will show:
Sensor Type
Enter to select a new Sensor Type, Default Range, Default Calibration Gas Value and Setpoints. Please see the Sensor Chart above for full details.
Sensor Range
Status LED Set Points
Relay ON / OFF Delays
Audible
Modbus ID
RS485 Baud Rate
Calibrate 4 mA Output
Calibrate 20 mA Output
Manual 4 - 20 mA Output
Used for testing purposes. The analog output can be set to a pre-determined value for system testing. Once the Menu is exited, the analog output reverts back to normal operation and tracks the gas value.
Exit Programming and Calibration Menus
Temperature Sensor Calibration
There is no calibration needed for the Temperature Sensor. The VP-TX120-SS has been programmed with a Steinhart equation for calculating the temperature value based on the Thermistor reading and Thermistor Beta value (B 0/50 = 3380). A 1% Thermistor is used and typically the accuracy is +/- 1 °C over the operating range of -20 to + 60 °C.
Humidity Sensor Calibration
There is no calibration required for the humidity sensor. The VP-TX120-SS has been programmed with the transfer function supplied with the Honeywell HIH series sensor. After Temperature compensation, the Humidity sensor is guaranteed to have an accuracy of +/- 3% RH from 5 to 95 % RH range, non-condensing.
Status LED
The Status LED shows the following:
GREEN = OK, RED (Flashing) = Sensor Fault, AMBER = Low Alarm, AMBER (Flashing) = Mid Alarm, RED = High Alarm
Audible
The Audible can be programmed either ON or OFF and is fixed to the HIGH alarm setting. If the Audible is enabled and ON, it can be silenced by pressing any pushbutton.
The Audible is also used as a pushbutton "Click". This feature is always enabled.
Function | Description |
---|---|
Function 03 | Read/Write Holding Registers |
Function 04 | Read Input Registers |
Function 06 | Write Single Registers |
Function 16 | Write Multiple Registers |
Function 03 Holding Registers
Address (Dec) | Address (Hex) | Function | Read/Write | Description |
---|---|---|---|---|
0000 | 0x00 | Gas Reading | Read Only | Real Time Gas Reading x Scaler |
0001 | 0x01 | Local Temperature Reading | Read Only | Real Time Temperature Reading in °C x 100 |
0002 | 0x02 | Local RH Reading | Read Only | Real Time Humidity Reading in %RH x 10 |
0003 | 0x03 | Gas Scaler | Read Only | 10 (Fixed) (500 Reading = 50 x 10) |
0004 | 0x04 | Sensors Present | Read Only | 0x0001 Gas Sensor Present 0x0002 Local Temperature Sensor Present 0x0040 Humidity Sensor Present A Value of 0x0003 = Gas and Temperature Sensors Present |
0005 | 0x05 | Product Version | Read Only | Firmware and Product ID |
0006 | 0x06 | - | - | Not Used |
0007 | 0x07 | - | - | Not Used |
0008 | 0x08 | - | - | Not Used |
0009 | 0x09 | - | - | Not Used |
0010 | 0x0A | - | - | Not Used |
0011 | 0x0B | - | - | Not Used |
0012 | 0x0C | - | - | Not Used |
0013 | 0x0D | Gas AD Counts | Read Only | Real Time A/D Counts (0 to 4096) |
0014 | 0x0E | Local Temperature AD Counts | Read Only | Real Time A/D Counts (0 to 4096) |
0015 | 0x0F | Local RH Reading AD Counts | Read Only | Real Time A/D Counts (0 to 4096) |
0016 | 0x10 | Push Button Satus | Read Only | 0x0000 = All OFF, 0x0001 = UP, 0x0002 = DOWN, 0x0004 = ENTER or combinations of above for 2 or 3 buttons combined |
0017 | 0x11 | - | - | Not Used |
0018 | 0x12 | - | - | Not Used |
0019 | 0x13 | - | - | Not Used |
0020 | 0x14 | Sensor Type | Read Only | 0 = NH3, 1 = Freon, 2 = CO, 3 = ALC, 4 = CH4, 5 = C3H8 |
0021 | 0x15 | - | - | Not Used |
0022 | 0x16 | Gas Sensor Zero | Read / Write | Zero AD Counts |
0023 | 0x17 | Gas Sensor Span | Read / Write | Span AD Counts |
0024 | 0x18 | Gas Sensor Cal Gas Value | Read / Write | Calibration Gas Value |
0025 | 0x19 | Gas Sensor Span Value | Read / Write | Span Value |
0026 | 0x1A | Reading Decimal Value | Read / Write | Decimals 0 = none, 1 or 2 |
0027 | 0x1B | Status LED Low | Read / Write | Low Set Point Value |
0028 | 0x1C | Status LED Mid | Read / Write | Mid Set Point Value |
0029 | 0x1D | Status LED High | Read / Write | High Set Point Value |
0030 | 0x1E | Status LED Differential | Read / Write | Differential Set Point Value |
0031 | 0x1F | - | - | Not Used |
0032 | 0x20 | Analog Output 4 mA | Read / Write | 4 mA DA Counts |
0033 | 0x21 | Analog Output 20 mA | Read / Write | 20 mA DA Counts |
0034 | 0x22 | - | - | Not Used |
Function 04 Input Registers
Address (Dec) | Address (Hex) | Function | Read/Write | Description |
---|---|---|---|---|
0000 | 0x00 | Gas Reading | Read Only | Real Time Gas Reading x Scaler |
0001 | 0x01 | Local Temperature Reading | Read Only | Real Time Temperature Reading in °C x 100 |
0002 | 0x02 | Local RH Reading | Read Only | Real Time Humidity Reading in %RH x 10 |
0003 | 0x03 | Gas Scaler | Read Only | 10 (Fixed) (500 Reading = 50 x 10) |
0004 | 0x04 | Sensors Present | Read Only | 0x0001 Gas Sensor Present 0x0002 Local Temperature Sensor Present 0x0040 Remote Temperature Sensor Present A Value of 0x0003 = Gas and Temperature Sensors Present |
0005 | 0x05 | Product Version | Read Only | Firmware and Product ID |
0006 | 0x06 | - | - | Not Used |
0007 | 0x07 | - | - | Not Used |