posting field values within few seconds fails

Using google app script I want to post measurements from my home domotics to a thingspeak channel. The chart has several charts.

I am using the following code

POST https://api.thingspeak.com/update.json

api_key=XXXXXXXXXXXXXXXX

field1=73

and after a few seconds

POST https://api.thingspeak.com/update.json

api_key=XXXXXXXXXXXXXXXX

field2=100.

In the channel it only updates the chart for field1. When I introduce a sleep of 15 seconds between the 2 posts, it will show both charts (field1 and field2). It seems not possible to send both posts with short intermediant times to update the both charts. Or should I use another way to achieve almost simultaneous updates of multiple charts ?

[theo koster]

The channel has several charts (typo)

Answer 1

[Hans Scharler]

The free ThingSpeak account tier has an update rate limit of 15 seconds.

You can send both field values in one update.

field1=73&field2=100

[theo koster]

Thanks that explains the behaviour