how to calibrate ultrasonic level transmitter

{"cid":"91191827","title":"Long Distance Ultrasonic Tank Level Sensor With Ultrasonic Level Transmitter","imgUrl":"https:\/\/img.ismap.com\/nimg\/44\/0b\/e3349ed3e0a3c8747cde237e63b1-200x200-1.jpg","attrs":{"Price":"Negotiable","Brand Name":"VACORDA","Model Number":"HKD","Minimum Order Quantity":"1 Piece\/Pieces","Certification":"ISO9001:2000\/CE","Place of Origin":"Sichuan, China (Mainland)","Supply Ability":"300 Piece\/Pieces per Month","Packaging Details":"Carton","Working Temperature":"-40\u2103~+75\u2103","Mode of Indication":"4 digit LCD","Material of sensor":"PVC\/PTFE","Accuracy":"0.2%Span (In air)","Medium temperature":"-40~80\u00b0C","Product name":"Factory Price Long Distance Ultrasonic Level Sensor Transmitter For Tank"}}

{"cid":"91188394","title":"Reliable explosion-proof ultrasonic level transmitter depth water measure with display","imgUrl":"https:\/\/img.ismap.com\/nimg\/47\/f3\/5e6dd15f68d291a43a5016d272a4-200x200-1.jpg","attrs":{"Price":"$80.00 - $200.00\/pieces","Brand Name":"KACISE","Model Number":"KUM","Minimum Order Quantity":"1PCS","Delivery Time":"5-8 work days","Place of Origin":"CHINA","Model":"explosion-proof ultrasonic level transmitter","Type":"Split \/ seperated type","feature":"explosion-proof ultrasonic level transmitter","Packaging Details":"each unit has individual box and all boxes are packed in standard packages or customers requests available","Port":"Xi'an or other","Supply Ability":"1000 Piece\/Pieces per Week negotiable","Certification":"CE"}}