You never mentioned sensor 2, you did say payloads.
How is sensor 1 distinguished from sensor 2.
More info is required, i.e an example of the incoming messages.
[edit
Try some thing like this you will need to give your sensors a topic or use a message property to distinguish
[{"id":"3e89f279.e1b5fe","type":"inject","z":"c74669a0.6a34f8","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"sensor1","payload":"10","payloadType":"str","x":110,"y":4380,"wires":[["a3d6b52b.7a83e8"]]},{"id":"a3d6b52b.7a83e8","type":"join","z":"c74669a0.6a34f8","name":"","mode":"custom","build":"object","property":"payload","propertyType":"msg","key":"topic","joiner":"\\n","joinerType":"str","accumulate":false,"timeout":"","count":"2","reduceRight":false,"reduceExp":"","reduceInit":"","reduceInitType":"","reduceFixup":"","x":250,"y":4400,"wires":[["48476a0e.c3b83c"]]},{"id":"a8b836c2.280f78","type":"inject","z":"c74669a0.6a34f8","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"sensor2","payload":"20","payloadType":"str","x":110,"y":4440,"wires":[["a3d6b52b.7a83e8","c57b5533.ce2c2"]]},{"id":"48476a0e.c3b83c","type":"change","z":"c74669a0.6a34f8","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"payload.sensor1","tot":"msg"},{"t":"set","p":"topic","pt":"msg","to":"sensor1","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":430,"y":4380,"wires":[["c57b5533.ce2c2"]]},{"id":"c57b5533.ce2c2","type":"debug","z":"c74669a0.6a34f8","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":650,"y":4380,"wires":[]}]
And this one will make sure sensor 1 arrives before sensor 2
[{"id":"3e89f279.e1b5fe","type":"inject","z":"c74669a0.6a34f8","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"sensor1","payload":"10","payloadType":"str","x":110,"y":4380,"wires":[["a3d6b52b.7a83e8"]]},{"id":"a3d6b52b.7a83e8","type":"join","z":"c74669a0.6a34f8","name":"","mode":"custom","build":"object","property":"payload","propertyType":"msg","key":"topic","joiner":"\\n","joinerType":"str","accumulate":false,"timeout":"","count":"2","reduceRight":false,"reduceExp":"","reduceInit":"","reduceInitType":"","reduceFixup":"","x":250,"y":4400,"wires":[["6df8c23e.1673fc"]]},{"id":"a8b836c2.280f78","type":"inject","z":"c74669a0.6a34f8","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"sensor2","payload":"20","payloadType":"str","x":110,"y":4440,"wires":[["c57b5533.ce2c2","a3d6b52b.7a83e8"]]},{"id":"6df8c23e.1673fc","type":"switch","z":"c74669a0.6a34f8","name":"","property":"topic","propertyType":"msg","rules":[{"t":"eq","v":"sensor2","vt":"str"}],"checkall":"true","repair":false,"outputs":1,"x":400,"y":4400,"wires":[["48476a0e.c3b83c"]]},{"id":"c57b5533.ce2c2","type":"debug","z":"c74669a0.6a34f8","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":590,"y":4480,"wires":[]},{"id":"48476a0e.c3b83c","type":"change","z":"c74669a0.6a34f8","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"payload.sensor1","tot":"msg"},{"t":"set","p":"topic","pt":"msg","to":"sensor1","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":570,"y":4400,"wires":[["c57b5533.ce2c2"]]}]
]