Simple Frequency to Voltage circuit

Frequency-to-Voltage converter circuit can use LM331
(Precision Voltage-to-Frequency Converters) by circuit below
But out put form pin 1 of lm331 is current so we must be careful
Input impredance of circuit that connected with this circuit

Fin 10kHz full scale
Vout = Fin * 2.09V*(RL/Rs)*(Rt*Ct)