DVM_RES_MEAS1.CIR * * VB VB 20 0 9VDC RB 20 21 1k * R_REF R_REF 21 22 1K * * RX - UNKNOWN RESISTOR RX 22 0 10 * * DIFF AMP - REFERENCE, R_RES E_REF 12 0 21 22 +1.0 * * DIFF AMP - UNKNOWN RES, RX E_RX 11 0 22 0 -1.0 * * CONTROL: VCNTRL=0 S1=ON, S2=OFF * VCNTRL=1 S1=Off,S2=ON VCNTL 15 0 PWL(0MS 0V 10MS 0V 10.01MS 5V) * * INTEGRATOR S1 11 1 15 0 SWB S2 12 1 31 0 SWA R1 1 2 100K C1 2 3 0.10UF IC=0V XOP1 0 2 3 OPAMP1 * * COMPARATOR (ZERO CROSSING DETECTOR) XCMP1 3 0 5 COMP1 * * AND GATE, S2 = ON IF VCNTRL AND XCMP1 OUTPUTS ARE HI VCC 30 0 DC 5V R31 30 31 10k D31 31 15 D1N4148 D32 31 5 D1N4148 * * * SUBCIRCUITS AND MODELS *********************************** * .SUBCKT COMP1 1 2 5 * TERMINALS: 1-INPUT+, 2-INPUT-, 5-OUTPUT * DIFF AMP EDIFF 3 0 VALUE = { V(1) - V(2) } * FREQUENCY RESPONSE RP1 3 4 500 CP1 4 0 1000PF * LIMITER EOUT 5 0 TABLE {V(4)} = (-0.5MV 0V) (0.5MV, 5V) .ENDS * * * OPAMP MACRO MODEL, SINGLE-POLE WITH 15V OUTPUT CLAMP * connections: non-inverting input * | inverting input * | | output * | | | .SUBCKT OPAMP1 1 2 6 * INPUT IMPEDANCE RIN 1 2 10MEG * DC GAIN=100K AND POLE1=100HZ * UNITY GAIN = DCGAIN X POLE1 = 10MHZ EGAIN 3 0 1 2 100K RP1 3 4 100K CP1 4 0 0.0159UF * OUTPUT BUFFER AND RESISTANCE EBUFFER 5 0 4 0 1 ROUT 5 6 10 .ENDS * .MODEL SWA VSWITCH(VON=5 VOFF=0 RON=1 ROFF=1e12) .MODEL SWB VSWITCH(VON=0 VOFF=5 RON=1 ROFF=1e12) * * DIODE .model D1N4148 D(Is=0.1p Rs=16 CJO=2p Tt=12n Bv=100 Ibv=0.1p) * * ANALYSIS ************************************************* .TRAN 25US 20MS UIC *.TRAN 0.1US 2000US UIC* .PROBE .END