TC_PREAMP.CIR - THERMOCOUPLE PREAMPLIFIER * * T MEASURE JUNCTION (deg C) V_TJUNC 10 0 PWL(0MS 0 100MS 100) RD10 10 0 1MEG * * T REFERENCE JUNCTION (deg C) V_TREF 11 0 PWL(0MS 22 100MS 22) RD11 11 0 1MEG * * J THERMOCOUPLE (V) X_TC1 10 11 0 1 TC_J_1 R1 1 4 5269 * * COLD JUNC - IC TEMP SENSOR (10MV/ DEG K) E_VSENSOR 0 2 VALUE = { 2.73 + V(11)*0.010 } R2 2 4 1000k * * OFFSET VOLTAGE VOFF 3 0 DC 2.73 R3 3 4 1000K * * FEEDBACK R RF 4 5 100K * * OPAMP XOP1 0 4 5 OPAMP1 * * *** J THERMOCOUPLE SUBCIRCUIT ************************************ * T_JUNC(C) - 1 T_REF(C) - 2 V_TC+(V) - 3 V_TC-(V) - 4 * .SUBCKT TC_J_1 1 2 3 4 * * USE POLYNOMIAL EQN TO FIND V VS. T (REF TO 0 DEGC) AT BOTH JUNC AND MEAS TEMPS. * V = B1*T + B2*T^2 + ... * * V_TJ - JUNCTION EMF (MV) VS. TEMP (C) E_TJ 5 0 VALUE = { + 0.503811878150E-01*V(1) + 0.304758369300E-04*V(1)**2 + + -0.856810657200E-07*V(1)**3 + 0.132281952950E-09*V(1)**4 + + -0.170529583370E-12*V(1)**5 + 0.209480906970E-15*V(1)**6 + + -0.125383953360E-18*V(1)**7 + 0.156317256970E-22*V(1)**8 } * * V_TR - REFERENCE EMF (MV) VS. TEMP (C) E_TR 6 0 VALUE = { + 0.503811878150E-01*V(2) + 0.304758369300E-04*V(2)**2 + + -0.856810657200E-07*V(2)**3 + 0.132281952950E-09*V(2)**4 + + -0.170529583370E-12*V(2)**5 + 0.209480906970E-15*V(2)**6 + + -0.125383953360E-18*V(2)**7 + 0.156317256970E-22*V(2)**8 } + * THERMOCOUPLE OUTPUT: * V_TC = V_TJ - V_TR * DIVIDE BY 1000 TO CONVERT MV TO V * E_TC 3 4 VALUE = { (V(5)-V(6))/1000 } * .ENDS ****************************************************************** * * OPAMP MACRO MODEL, SINGLE-POLE * connections: non-inverting input * | inverting input * | | output * | | | .SUBCKT OPAMP1 1 2 6 * INPUT IMPEDANCE RIN 1 2 10MEG * GAIN BW PRODUCT = 10MHZ * DC GAIN (100K) AND POLE 1 (100HZ) EGAIN 3 0 1 2 100K RP1 3 4 1K CP1 4 0 1.5915UF * OUTPUT BUFFER AND RESISTANCE EBUFFER 5 0 4 0 1 ROUT 5 6 10 .ENDS **************************************************************** * * ANALYSIS .TRAN 1MS 100MS * VIEW RESULTS .PROBE .END