Model 470 Digital Pressure Transducers 1
Contents SECTION ONE: Introduction ..................................................................................................... 3 1.1 About the Setra 470 ............................................................................................................ 3 1.2 About this Manual................................................................................................................ 4 SECTION TWO: Installing the Model 470 ................................................................
SETRA Model 470 Digital Pressure Transducer SECTION ONE Introduction 1.1 About the Setra 470 The Setra 470 Digital Pressure Transducer is a highly accurate pressure measurement system utilizing the patented SETRACERAM sensor, advanced micro-computer based electronics, and sophisticated firmware, resulting in a 0.02% F.S. system accuracy traceable to the National Institute of Standards and Technology. The Setra 470 accurately measures and reports barometric pressure.
1.2 About this Manual This manual contains information you need to use the Setra 470. Whenever possible, the information is presented in nontechnical language so that you can install and use the transducer without any specialized training. However, the Setra 470 can be used in a wide variety of data acquisition systems, laboratories, calibration labs, and digital weather systems.
SECTION TWO Installing the Model 470 2.1 Power Connections The Setra 470 requires a 5 volt DC power supply regulated to ±1% which can supply 90 milliamps of current. Use of a correctly rated and regulated power supply is important for correct operation of the digital electronics in the Setra 470. To apply power to the Setra 470, follow these steps: 1.
If it does not, (i.e. if the computer also has a DTE interface, and therefore transmits on its own pin 2, and receives on its own pin 3), a “reversing” or “null modem” cable is required for connection. This is simply a cable which connects pin 2 and 3 of the Setra 470 to pins 3 and 2 of the computer respectively. This kind of cable is commercially available and is also available from Setra.
SECTION THREE Communications Interfacing 3.1 Communications Software Protocols The Setra 470 RS-232 communication port allows several rates of data transfer (baud rates) between the Setra 470 and the host device. Both devices must communicate at the same data rate. The factory default baud rate of the Setra 470 is 2400. Therefore, the device connected to the Setra 470 initially must also be set to 2400. To change the Setra 470 baud rate refer to Section 5.2.
3.4 Functions This summary of functions is provided for reference only. See the following sections for details on how to use each function. Command codes must be in capital letters. Function Name ASCII Hex Code Command Code ASCII Code PRINT P 80 $50 Report information to a computer or data acquisition system. 4.1 CONVERT U 85 $55 CONVERT engineering units being reported. 4.2 ZERO Z 90 $5A Perform relative or absolute tare value. 4.
— — 45 $2D Shuts off the function whose command code follows it. — CLEAR —C 45 67 $2D $43 Turn off MIN/MAX, clear the tare value, convert to the original engineering units. —MIN/MAX —M 45 77 $2D $4D Exit MIN/MAX tracking mode. 4.5 —CONV —U 45 85 $2D $55 Reverts to reporting data in the factory default pressure units. 4.2 —ZERO —Z 45 90 $2D $5A Clear any values being Zero/Tare’d from the reported reading. 4.8 —PRINT —P 45 80 $2D $50 Turn off repetitive print mode. 4.
ASCII Code ASCII Hex Code xUx * * 0 0 48 $30 The number 0. 1 1 49 $31 The number 1. 2 2 50 $32 The number 2. 3 3 51 $33 The number 3. 4 4 52 $34 The number 4. 5 5 53 $35 The number 5. 6 6 54 $36 The number 6. 7 7 55 $37 The number 7. 8 8 56 $38 The number 8. 9 9 57 $39 The number 9. Function Name USER DEFINED UNITS Command Code Description Enter conversion ratio for 4.3 non-standard engineering units in nonvolatile memory.
3.5 In Case of Error Messages The following summary explains the meaning of error messages that you may receive from the 470 in response to a command, and also tells you what actions to take in response to the error message. Message Explanation What to Do 1. “UNABLE” The transducer cannot accept or execute a number or function command it received, or you have attempted to execute a setup function or a pressure measurement function while the transducer is reporting data in units of altitude.
3.6 Symbols The following summary explains the meaning of symbols that may follow the data you receive from the 470 in response to a command. “OK” The data is within the requirement for the user defined STABILITY INDICATOR. “hPa” The data is reported in hectopascals. “PSI” The data is reported in pounds per square inch. “mbar” The data is reported in millibars. “mm Hg” The data is reported in millimeters of mercury. “in H2O” The data is reported in inches of water.
SECTION FOUR Precision Measurement Functions 4.1 Interrogation The most commonly used function of the Setra 470 is the PRINT or INTERROGATION command. To get a data reading from the transducer, follow this procedure. 1. Transmit P, for PRINT. 2. The transducer response is a series of characters consisting of the pressure reading (in whatever engineering units are currently selected) and other information.
3. The transducer deselects the engineering units currently in use, and selects the next engineering units in the sequence: hPa PSI mbar mm Hg in Hg mm H2O in H2O ft m units hectopascals pounds per square inch millibar millimeters of mercury inches of mercury millimeters of water inches of water feet meters user definable units 4. If you have disabled any of the engineering units using the function described in Section 5.3, those units are ignored.
9. If the response “NO CAL” is received, the program enable switch specified in Step 5 is not set to “ON”. Transmit C, for CLEAR, and restart this procedure from the beginning. 10. If the 470 responds “UNABLE”, the user defined units have been disabled by use of the DISABLE UNITS function (Section 5.3). Transmit C, for CLEAR, re-enable the user defined units (Section 5.3) and restart this procedure from the beginning. 11.
9. If the 470 responds “UNABLE”, the user defined units have been disabled by use of the DISABLE UNITS function (Selection 5.3). Transmit C, for CLEAR, re-enable the user defined units (Section 5.3) and restart this procedure from the beginning. 10. Transmit 5 alphanumeric characters, in any combination, to represent engineering units of the conversion. For example, if the transducer is currently reporting in PSI and the desired units are grams per square centimeter, the ratio is 70.
5. Transmit the new low setpoint, followed by S. 6. The 470 responds “PROTEC”. Set the program enable switch to “OFF” (Section 7.2). Transmit C, for CLEAR. 7. To examine the current value of the setpoints, transmit SP, for a SETUP summary report (Section 4.10). For example, to set the high setpoint to 15.0010 and low setpoint to 14.0010, transmit: SA15.0010S14.0010S 4.
For example, to subtract 10 from the reading, transmit: 10Z 3. To add an offset to the reading, transmit -, the minus sign, followed by the amount of the offset, followed by Z, for ZERO. The Setra 470 saves the negative offset as a tare value and subtracts it from every subsequent reading. In response to an interrogation (Section 4.1) the 470 response contains the letter “T”, for Tared Pressure, rather than “A”, absolute pressure. For example, to add 10 to the reading transmit: -10Z 4.
2. The transducer reports a sequence of information which indicates the status of any functions which are currently in use and some blank lines, as shown in this example: STATUS: Elev: Max: Min: HI A: LO A: Zero: Stab: Unit: 256 FT. 14.4193 PSI A 14.5188 PSI A 15.8000 PSI A 11.0000 PSI A 1.0000 PSI A 0.0005 PSI A 1 PER PSI In the example above: “Elev” shows the DASI station elevation (Section 4.11). “Max” and “Min” show the maximum and minimum pressures applied to the sensor (Section 4.
4. Transmit S, for SETUP. 5. If the elevation was in meters, transmit U, for CONVERT. 6. Transmit S, for SETUP. For example, if the station elevation is 1023 feet, transmit: SB1023SS Or, if the station elevation is 237 meters, transmit: SB237SUS 7. The Setra 470 is now in DASI mode and reports barometric pressure reduced to sea level in response to an INTERROGATION command, indicated by “SEA LEVEL”. 8.
SECTION FIVE Setup Functions 5.1 Status After Power is Applied The Setra 470 has an internal nonvolatile memory for storing certain status and calibration information. This memory is not erased when power is removed from the unit. Some functions (such as baud rate, alarm setpoints, and user conversion factors) are stored in this memory. Once they are setup they do not need to be setup again unless you wish to change the configuration.
2. Transmit -5555S. This is the baud rate access code. 3. Transmit the new baud rate. The Setra 470 supports 300, 600, 1200, 2400, 4800, or 9600 baud. If the 470 responds “CAL BR”, the baud rate is not supported, repeat this step. 4. Transmit S For example, to change the baud rate of the transducer to 9600, transmit: -5555S9600S 5. Adjust the baud rate of the computer or terminal being used to communicate with the Setra 470 at the new rate. B) This just entered baud rate is used by the 470 until power-down.
5. Transmit a sequence of 1’s and 0’s in which each 1 or 0 corresponds to an engineering unit of measure in the sequence listed below. Transmit a 1 to enable, or a 0 to disable, selection of the corresponding units. The sequence of units is: “units” (the user programmable units) hPa PSI mbar mm Hg in Hg mm H20 in H20 feet meters Each 1 or 0 must be followed by an S, for SETUP.
3. Transmit a sequence of 1’s and 0’s in which each 1 or 0 corresponds to an engineering unit of measure in the sequence listed below. Transmit a 1 to enable, or a 0 to disable, selection of the corresponding units. The sequence of units is: “units” (the user programmable units) hPa PSI mbar mm Hg in Hg mm H20 in H20 feet meters Each 1 or 0 must be followed by an S, for SETUP.
8. Transmit C, for CLEAR. 9. The Setra 470 next reports the VERIFY message described in Section 5.7 and executes the internal start-up procedure for thirty seconds. When the start-up procedure is complete, the transducer again reports VERIFY message. It is not possible to interrogate or perform any other function with the Setra 470 before you receive the second VERIFY message. 5.6 Software Revision Number The Setra 470 internal software is stored internally in a PROM (Programmable Read Only Memory).
To change the Stability Indicator Limit, use the following procedure: 1. Use the CONVERT function (see Section 4.2) so that the 470 reports data in units of pressure in response to an interrogation. (i.e., the transducer should not be reporting in units of altitude.) 2. Transmit -1111S. This is the Stability Indicator access code. 3. Transmit the new stability limit in the engineering units which are now in use. 4. Transmit S. For example, to set the Stability Indicator to .001 psi, transmit: -1111S.
SECTION SIX Altitude Measurement Functions The Setra 470 Digital Pressure Transducer can report a variety of altitude measurements. It may be used as an altimeter calibrator, a standard altimeter, a true corrected altimeter (self corrected or remote), or as a relative altimeter. It may also be used to indicate small relative changes in altitude through the use of the zero/tare function. 6.
altitude in response to an interrogation as it is moved from one location to another. CAUTION: In any true altimetry application, the accuracy of the measurement depends on the quality of the correction made for local barometric pressure. Barometric pressure changes often, and so the reading drifts over time as the sea level corrected pressure drifts. To recalibrate the true altimeter, repeat the above procedure at the known starting elevation often. 6.
6.3 Relative Altitude Measurement The Setra 470 can measure relative altitude in either Standard or True Altimeter Mode. In this mode, the 470 reports altitude relative to a reference altitude which you establish by setting the reported altitude reading to zero, or by offsetting it to a higher or lower value by a specified amount. A) Follow this procedure to report relative altitude referenced to a zeroed starting point. 1. Put the transducer into an altitude reporting mode.
SECTION SEVEN Calibration 7.1 Calibration The zero and span of the Setra 470 Digital Pressure Transducer may be calibrated using the procedures in Section 7.2 - 7.4. A high accuracy primary pressure standard is recommended as the calibration source, since the high accuracy of the Setra 470 is adversely affected if the calibration pressure is not of greater accuracy.
7.3 Zero Calibration This procedure for recalibrating the zero point of the transducer can be aborted at any point by setting the program enable switch to off and transmitting C, to execute the CLEAR function. 1. Use the CONVERT function (see Section 4.2) so that the 470 reports data in units of pressure in response to an interrogation. (i.e., the transducer should not be reporting in units of altitude.) 2.
7.4 Span Calibration To perform the span calibration on the 470, it is necessary to apply both the zero and the full scale pressures, as described in the following procedure. This procedure can be aborted at any point by setting the program enable switch to “OFF” and transmitting C, to execute the CLEAR function. 1. Use the CONVERT function (see Section 4.2) so that the 470 reports data in units of pressure in response to an interrogation. (i.e., the transducer should not be reporting in units of altitude.
Appendix I Interface Program Example Following is an example of interfacing the Setra 470 to an IBM or compatible PC (Personal Computer). Although real applications for the 470 usually require more programming in specialized languages on different machines, the example is a simple BASIC program which shows the important parameters to setup in the PC to allow serial communications.
Specifications Pressure media: Clean dry nonconductive noncorrosive gas Accuracy: accuracy1 nonlinearity hysteresis nonrepeatability thermal zero shift2 thermal span shift2 altitude resolution stability, 24 hours stability, 30 days stability, 1 year ±0.02% full scale at 70°F (21°C) ±0.012% full scale (End point) 0.010% full scale ±0.010% full scale ±0.002% FS/°F (0.004% FS/°C) ±0.001% FS/°F (0.002% FS/°C) 1 ft. (4 ft. for 100 psi range) ±0.005% full scale ±0.02% full scale ±0.
Limited Warranty SETRA warrants its products to be free from defects in materials and workmanship, subject to the folloing terms and conditions: Without charge, SETRA will repair or replace products found to be defective in materials or workmanship within the warranty period; provided that: a) the product has not been subjected to abuse, neglect, accident, incorrect wiring not our own, improper installation or servicing, or use in violation of instructions furnished by SETRA; b) the product has not been
