error Bacnet read

[AngelesTR]

I'm using a Intesis router ip-mstp.
 192.168.100.246

I get read bacnet clients
246 - 192.168.100.246 -router
50001 - 192.168.100.246 - device mstp

But when I try to read objects I always have the same error: unknown object,

require('bacnet')

bacnet.deviceip = '192.168.100.246'

device_id = 50001
value,err = bacnet.readvalue(device_id, 'analog value',1086)
log(err)
  [size=1][size=1]*
[/size][/size]

Thanks