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DESCRIPTION

The INVALCO Model 705 Gas Flow Computer is a low cost, single loop, gas flow computer that incorporates three separate calculation choices dependent on application. The Model 705 accepts inputs from INVALCOʼs GT Series gas turbine meter and a wide range of other manufacturersʼ flow meters, such as vortex, orifice plate, averaging pitot tubes, and wedges.

Specifications

Display	Alphanumeric LCD display with backlighting and two lines x 20 characters/line. Each character is 5.5 mm high.
Keyboard	Sealed membrane keyboard with four keys.
Transducer Supply	8-24 Vdc field adjustable, 50 mA maximum (2-3V less than minimum input voltage).
Power Requirements	11.5 to 28.0 Vdc, 140 mA typical (no options). AC Mains: Set internally to 95-135 Vac or 190-260 Vac.
Operating Temperature	0 to 55 C
Facia	Watertight to NEMA 3S or IP65
Dimensions	5.7” (144 mm) wide x 2.8” (72mm) high x 7.4” (188mm) deep x 7.4” (188 mm) deep.
Panel Cutout	5.5” (139 mm) x 2.6” (67 mm).
Frequency Input Frequency Range: Input Circuits: K-Factor Range: Non-Linear Correction:	Minimum - 0.25 Hz on rate. 0 Hz on total. Maximum - 10 kHz. Will accept most sine, logic, and proximity switch inputs. 0.1000 to 50,000. Up to ten correction points.
4-20mA Inputs Inputs: Input Impedance: Accuracy: Circuit:	Two each, pressure and temperature (705A option). 250 ohms. 0.05% The 250 ohm resistors are connected to a common signal ground (current sinking)
RTD Input (Model 705R) Temperature Measurement Range:	-148°F to 392°F (-100°C to 200°C). Note: A wider temperature range can be handled via a 4-20 mA input.
Approvals Accuracy: RTD Type: Linearity:	Canadian Standards Association (CSA) pending CE compliant. 0.1°C Platinum PT100, two, three, or four-wire. The non-linearity of the RTD is internally compensated for.
Pressure Input Type: Span: Atmospheric:	Absolute or gauge. The absolute or gauge pressure at both 4 mA and 20 mA is programmable. If a gauge pressure sensor is used, the atmospheric pressure can be programmed.
Pulse Output Pulse Width: Duty Cycle: Output:	10 mSec (negative going pulse). Maximum of 49 pulses per second. An open-collector transistor will sink 100 mA maximum. The pulse output is suitable for driving remote counter or PLCʼs.
RS232/485 Option Type: Function: Printer: Computer: Baud Rate: Data Bits: Parity: Data Logging Time:	RS232 four wire RS422 and two wire RS485 are provided. When using the RS422/485, multipoint communication can be implemented with up to 32 instruments connected to a common bus. Printer and computer protocols are fully programmable. A print is initiated on each reset or at a programmable time interval. Protocols are provided for roll and column printers. An ASCII-based protocol enables all displayed parameters to be read and the totals to be reset. 300 to 9,600. Seven or eight. None, odd, or even. Output generated at intervals of once a minute to once every 24 hours. The totals can be programmed to reset on each print or at 24:00 hours. A real-time clock is provided to give time and date on each output.
4-20mA Output Option Function: Resolution: Accuracy: Maximum Load: Isolation:	The flow rate, mass, corrected volume, or energy is output. The 4 mA and 20 mA points can be programmed to provide a fully-scaled output. Ten bits. Better than 0.1%. Voltage Burden: 5V;500 ohms internally powered.; 950 ohms from external 24 Vdc Output is isolated
Relay Output Option Function: Maximum Switching Power: Maximum Switching Voltage: Maximum Switching Current:	High and low flow rate alarms based on the flow rate, mass, corrected volume, or energy. 250 VA 250 Vac, 30 Vdc 5 Amps
Ideal Gas Display: Temperature Range: Pressure Range:	Corrected volume (ft3 or m3). Mass (lb or kg). -450°F to 800° F (-237°C to 450°C). 0 kPa abs (0 psia) to 100,000 kPa abs (10,000 psia).
General Gas Gases: Compressibility: Temperature Range: Pressure Range:	Handles most gases for which the critical temperature, pressure, and specific gravity are known. Calculated using the Redlich-Kwong equation. -450°F to 800°F (-273° C to 450°C). (RTD has a more limited range.) 0 psia abs (0 kPa) to 10,000 psia abs (100,000 kPa).
Natural Gas Calculations: Temperature Range: Specific Gravity Range: Carbon Dioxide: Nitrogen:	Uses NX-19 equation to calculate supercompressibility FPV. -40°F to 240°F (-40°C to 115°C) 14.69 psia abs (101.325 kPa) to 4,85 psia abs 0.554 to 1.000. 0 to 15% mole. 0 to 15% mole.

FEATURES

- Backlit alphanumeric LCD display of Mass Flow,
- Corrected Volume, and Energy Flow.
- Accepts frequency and 4-20 mA flow inputs
- Temperature and pressure compensation.
- Ten-point non-linearity correction.
- 4-20 mA analog output, optional.
- Pulse output for remote counters.
- Data logging output, optional.
- RS232/422/485 Serial Communication Option

OPERATION

The Model 705 Gas Flow Computer incorporates compensation for gas and vapor to the following equations:
1. Ideal Gas Law using temperature and pressure correction, but where compressibility correction is not required.
2. General Gases where compressibility is calculated using the Redlich-Kwong1 state equation. This equation is suitable for gases which have known properties.
3. Natural Gas using the NX-19 equation to calculate supercompressibility.
The backlit alphanumeric display simplifies programming and provides a clear indication of all parameters, as well as engineering units. The Model 705 is fully programmable and all operating parameters are entered via the front panel keyboard.
A scaled output suitable for driving remote totalizers is a standard feature, while options include an isolated 4-20 mA retransmission, high and low flow alarms, and an RS232/422/485 output.
The pulse output, 4-20 mA retransmission, and alarms will operate on either the mass, corrected volume, or energy outputs, depending on which value is programmed as the default display. The RS232/422/485 option will output all parameterswhich are displayed and protocols are provided for standard roll and column printers as well as for computer interface. (A real-time clock on the RS232/422/485 board provides time and date.
A unique feature available with the RS232/422/485 output is the ability to print flow rates and totals at programmable time intervals. This enables the instrument to function as a data logger when used in conjunction with a printer or other storage device. The totals can be programmed to reset via the front panel after each print or at 24:00 hours. Two versions of the instrument are available: Model 705R with direct RTD temperature input and Model 705A with a 4-20 mA temperature input.
Both versions require a 4-20 mA input of pressure, either absolute or gauge.

PARAMETERS DISPLAYED

Information is displayed in a number of display windows which are selected using the Display key.

General
Flow rate of the mass or corrected volume is displayed in units per day, hour, minute, or second Total of the mass or corrected volume. A reset key on the front panel enables totals to be reset or the key can be disabled during setup. Totals are displayed with eight digits.

Gas Flow
- Corrected Volume at base conditions (ft3 or m3).
- Mass (lb or kg).
- Temperature (°F or °C).
- Pressure (psi or kPa) in absolute or gauge
- Compressibility Z, for general gases.
- Supercompressibility FPV for natural gas (NX-19).

ADDITIONAL INFORMATION

Note: Dimensions-Inches to the nearest tenth (millimeters to the nearest whole mm), each independently dimensioned from respective engineering drawings.