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CDI Universal Evaluation Board Designed For Use With The GE/NovaSensor Pressure Sensors Series NPC-1210 and NPH-8 FEATURES: • Instant Prototyping • Selectable Voltage Outputs • Pressure Ranges From 10”H20 to 100 psig or psia • Compatible with the NPC-1210 and NPH-8 Sensors INTRODUCTION: The CDI Universal Evaluation Board has been designed for use with the GE/NovaSensor pressure sensors series NPC-1210 and the NPH-8. The board is intended to expedite the bread boarding of almost all pressure sensor applications. While the board will come pre-calibrated for an output of 0.5 V to 4.5 V for any pressure range between 10” water to 100 psi, the user can easily change the output by recalculating the gain, and changing a couple of resistors. Below you will find a general description and examples. GENERAL CIRCUIT DESCRIPTION: To explain how the CDI Universal Evaluation Board works, the circuit is shown in Figure 1, and is broken down into three sections. Vss SENSOR SELECTION: Connecting the solder shorts The first step in using the CDI Universal Evaluation Board is to make sure that the correct solder shorts are connected. Referring to schematic diagram, shown in Figure 1, as the sensor to be used is a NPC1210 device, solder shorts S1, S2, S3 and S4 should be shorted via Solder blobs. (Solder Shorts S5, S6, S7 and S8 are only used if an NPH-8 pressure sensor is used. Vss R1 10K ohm LT1004‐1.2 Vss 2 V1 3 U1 2 8 LT1490 4 Section 3 7 1 1 S1 U2 R5 4 Rset R3 1 NPC S3 3 U3 LT1789 Vo= 0.5 to 4.5 V 6 G = 26 to 160 Span Adj 8 3 5 4 S2 2 R2 820 ohms LT1490 R4 5 5 S5 V1 6 7 S4 R6 10 S7 Section 1 NPH 4 S6 Section 2 6 S8 Figure I Page 1 www.cdiweb.com 1-800-777-7334 email: [email protected] Offset Adj 10K ohm 2.5K ohm CDI Universal Evaluation Board Designed For Use With The GE/NovaSensor Pressure Sensors Series NPC-1210 and NPH-8 Vss SECTION 1: THE CURRENT SOURCE Vss R1 This portion of the circuit sets current to the pressure sensor. The NPC and NPH-8 series sensors should be driven by a 1.5mA constant current source to achieve the specified output voltages as shown on the datasheet, the Iset current is set by the Linear Technology 1.2V voltage reference and R2. The exact value of Iset will equal: 10K ohm Section 3 2 V1 LT1004‐1.2 Vss 3 2 U1 7 8 LT1490 4 1 1 S1 R5 4 U2 Rset R3 1 Vo= 0.5 to 4.5 V 6 G = 26 to 160 8 3 NPC S3 U3 LT1789 Span Adj 5 3 4 S2 2 R2 820 ohms LT1490 Offset Adj R4 10K ohm 5 5 S5 V1 6 7 S4 2.5K ohm R6 10 S7 Iset = V1/R2 = 1.2V/820 ohms ≈ 1.5 mA Section 1 S6 4 NPH Section 2 6 Figure I S8 Other values of the Iset are possible by adjusting the R2 resistor value. Please note that the output of the NPC and NPH-8 devices are ratiometric to the supply current. For instance, the value of R2 is changed from the datasheet. The specified 1.5 mA such that Iset = 0.75 mA, then the output of the sensor will be ½ of the specified output shown on the datasheet. SECTION 2: Vss Section 2 of the circuit is simply a divider network which sets the offset to the output. The Universal Evaluation Board will be factory set to 0.5 V. This offset is not part of the amplifier circuit and should not be interactive with the gain adjustment. Vss R1 10K ohm Section 3 2 V1 LT1004‐1.2 Vss 3 2 U1 7 8 LT1490 4 1 1 S1 U2 R5 4 Rset R3 1 NPC S3 3 U3 LT1789 8 3 5 4 S2 2 R2 820 ohms LT1490 R4 5 5 S5 V1 6 7 S4 You can adjust the amount of offset injected into the circuits within the voltage divider limits. R6 10 S7 Section 1 NPH 4 S6 Section 2 6 S8 Figure I Page 2 www.cdiweb.com Vo= 0.5 to 4.5 V 6 G = 26 to 160 Span Adj 1-800-777-7334 email: [email protected] Offset Adj 10K ohm 2.5K ohm CDI Universal Evaluation Board Designed For Use With The GE/NovaSensor Pressure Sensors Series NPC-1210 and NPH-8 SECTION 3: The heart of the CDI Universal Evaluation board is shown in section 3. The Linear Technology LT1789-10 is a micro-powered, single source instrumentation amplifier. The gain is normally set by a single resistor, however in this circuit, two resistors are used: A fixed resistor and potentiometer. This manner allows for some gain adjust due to variation in the pressure sensors output and Iset current source. For a complete understanding of the LT1789, it’s strongly suggested that the Linear Technology datasheet for that device be reviewed. The gain of the LT1789-10 is set by the value of resistor RG, applied across pins 1 and 8. For the LT1789-10, the gain G will be Vss G =10 • (1 + 200k/RG) Therefore the value of Rg can be calculated from the desired gain by Vss R1 10K ohm LT1004‐1.2 Vss 2 V1 3 2 U1 8 4 1 1 LT1490 S1 U2 Rg = 200k/(0.1 • G – 1) R5 4 Rset R3 1 NPC S3 From the NPC and NPH-8 datasheet, the sensor can have various outputs, so Rg needs to be able to achieve any of these values. Section 3 7 3 U3 LT1789 Vo= 0.5 to 4.5 V 6 G = 26 to 160 Span Adj 8 3 5 4 S2 2 R2 820 ohms LT1490 R4 5 5 S5 V1 6 7 S4 R6 10 S7 Section 1 NPH 4 S6 Section 2 6 S8 Figure I Page 3 www.cdiweb.com 1-800-777-7334 email: [email protected] Offset Adj 10K ohm 2.5K ohm CDI Universal Evaluation Board Designed For Use With The GE/NovaSensor Pressure Sensors Series NPC-1210 and NPH-8 Below is a chart showing the potential value of Rg: NPC-1210 Low Pressure Output Span Gain (4/Output) Rset (Ohms) Min 0.025 4 160.0 13333 Typical 0.05 4 80.0 28571 Max 0.07 4 57.1 42424 Output Span Gain (4/Output) Rset (Ohms) Min 0.075 4 53.3 46154 Typical 0.1 4 40.0 66667 Max 0.15 4 26.7 120000 Output Span Gain (4/Output) Rset (Ohms) Min 0.05 4 80.0 2532 Typical 0.075 4 53.3 3822 Max 0.15 4 26.7 7792 Output Span Gain (4/Output) Rset (Ohms) Min 0.075 4 53.3 3822 Typical 0.1 4 40.0 5128 Max 0.125 4 32.0 6452 Output Span Gain (4/Output) Rset (Ohms) Min 0.075 4 53.3 3822 Typical 0.1 4 40.0 5128 Max 0.125 4 32.0 6452 NPC-1210 Medium Pressure NPH-8-007xH Low Pressure NPH-8-030xH Low Pressure NPH-8 Medium Pressure The resistor value for the two resistors is on the Universal Evaluation Board. They are chosen such that, the fixed resistor is 80% of the values (most of the gain) and the potentiometer can be used to trim the gain to the exact requirements. Page 4 www.cdiweb.com 1-800-777-7334 email: [email protected] CDI Universal Evaluation Board Designed For Use With The GE/NovaSensor Pressure Sensors Series NPC-1210 and NPH-8 ORDERING INFORMATION: When ordering the CDI Universal Evaluation Board, please use the chart below. UPEB Sensor Type NPC NPH Pressure Range 010 Inches water column 001 PSI 005 PSI 015 PSI 030 PSI 050 PS1 100 PSI Pressure Reference D G A UPEB ‐ XXX ‐ XXX ‐ X 3 inches 0.25” Component Distributors Inc. www.cdiweb.com U1 R1 0.25” U2 P1 2 Inches R4 Offset Adj R2 U3 R3 R5 Span Adj P2 Vout Vin Gnd PressEval01 – Rev A Note: If you would like a non-standard pressure range, or the device to be calibrated in different units please contact CDI directly at 1-800-777-7334 or [email protected] and talk with a FAE before ordering. Page 5 www.cdiweb.com 1-800-777-7334 email: [email protected]