is my SEN0219 giving normal output? See graph

Hello,

I am using the following code and it appears this sensor is all over the place!!

I decided to map out the data points to try and figure out what i was seeing. The data in the serial monitor seemed very erratic. Does my sensor have issues or is this normal? I thought these things were supposed to be accurate lol. Please help!

GRAPH: https://imgur.com/a/WKT2S



Arduino Sketch Code:

---------------------------------------------------------------

int sensorIn = A3;

void setup(){
Serial.begin(9600);
// Set the default voltage of the reference voltage
// analogReference(DEFAULT);
}

void loop(){

String CO2PPM;
CO2PPM = CO2Read();
Serial.println(CO2PPM);
delay(2);
}

String CO2Read(){
//Read voltage
int sensorValue = analogRead(sensorIn);

// The analog signal is converted to a voltage
float voltage = sensorValue*(5000/1024.0);
if(voltage == 0)
{
Serial.println("Fault");
}
else if(voltage < 400)
{
Serial.println("preheating");
}
else
{
int voltage_diference=voltage-400;
float concentration=voltage_diference*50.0/16.0;
return String(concentration);
}
}

-------------------- Python Pandas Plotting Code-------------------------------------------------

import pandas as pd

df = pd.read_csv('/home/myuser/co2.log', parse_dates=True, index_col=0, names = ['timestamp', 'co2reading'])

ax = df.plot(figsize=(40,10))
fig = ax.get_figure()
fig.savefig('asdf.png')


---------------------Python Script Write Data to file from Serial Out -----------------------------

## import the serial library
import serial
from time import localtime, strftime, sleep

## Boolean variable that will represent
## whether or not the arduino is connected
connected = False

## establish connection to the serial port that your arduino
## is connected to.

#locations=['/dev/ttyUSB0','/dev/ttyUSB1','/dev/ttyUSB2','/dev/ttyUSB3']
locations=['/dev/ttyACM0','/dev/ttyACM1','/dev/ttyACM2','/dev/ttyACM3']

for device in locations:
try:
print "Trying...",device
ser = serial.Serial(device, 9600)
break
except:
print "Failed to connect on",device

## loop until the arduino tells us it is ready
while not connected:
serin = ser.read()
connected = True

## open text file to store the current
text_file = open("/home/myuser/co2.log", 'w+')


counter = 0
while True:
if ser.inWaiting():
counter +=1
x = ser.readline()
x = x.decode('utf-8', 'ignore').encode("utf-8")
mytime = strftime("%Y-%m-%d %H:%M:%S", localtime())
msgformat = '{},{}'.format(mytime, x)
if counter > 500:
text_file.write(msgformat)
print msgformat
text_file.flush()
else:
print 'waiting'
continue

if x=="\n":
text_file.seek(0)
text_file.truncate()

## close the serial connection and text file
text_file.close()
ser.close()