stalker 2.3_Analog Input Signal

Project: Real Time in Collecting Water level data using 4-20mA ultrasonic sensor

Initial Objective : to read current level signal
Problem : I am using signal injector to simulate 0-5v to analog A0 pin. My problem is, voltage reading at pin A0 (measured using multimeter) is not equivalent when showing at serial monitor in arduino sketch program. The code as below;

void setup()
Serial.print(“ssVoltage is:; “);
void loop()
// read the input on analog pin 0:
int sensorValue = analogRead(A0);
float voltage=sensorValue*4.998/1024; // actual volt from signal injector
Serial.println(” ssV;”);
delay(1000); // delay in between reads for stability

Signal Injector Serial Monitor
0.0V 0.0V
0.5V 0.75V
1.0V 1.5V
1.5V 2.25V
2.0V 3.0V
2.5V 3.75V
3.3V 4.98V look like maximum bit 1024 at 3.3V
3.5V 4.98V
4.0V 4.98V
4.5V 4.98V
4.99V 4.98V

Pls advice

The input is 3.3v MAX, so 3.3/1023.