scaling

[machinemaker 0]

I am using a Micrologix 1400. My HMI is putting out a number 0 to 60 representing the speed of a motor in HZ. I want to scale it in the plc to drive a analog output. I believe the output is from 0 to 32767. tried using SCL but can not get it to work. Obviously I do not have the right numbers or using the wrong instruction. Help. I could just simply multiply HZ by 546?

[Ken Roach 194]

I always write out my scaling units and datatypes longhand so I'm sure I'm getting it right. You have a value from 0 to 60 representing Hertz. Is that an integer value or a Floating-Point value ? You want to put out an analog signal that also represents Hertz, but across the full scale of the analog module. For example, this would make 60 Hz = 10 V. Is this correct ? Exactly what model of Analog module are you using ? For the popular 1762-OF4 module, you can select a "raw/proportional" or a "scaled for PID" mode. In the "raw/proportional" mode, the full scale is actually the hard limit output of the channel, which is 10.5 volts, not 10.0 volts. From RA Knowledgebase article 34193, an excerpt: Raw/Proportional Data Table Value Voltage/Current Value 32767 10.5 Volts 31206 10 Volts 0 0 Volts 32767 21 mA 31206 20 mA 6241 4 mA 0 0 mA

[machinemaker 0]

Sorry, forgot to say I am using the analog outputs located on the PLC itself. I was trying to scale the 0 to 60. Yes those numbers are integer values. 60HZ would be a full 10v output (32767).

[Mickey 71]

The embedded analog out on your ML1400 is 12 bit 0-4095 = 0-10volts. Use the "SCP" instruction for your scaling see pictures below. ( your input address may vary) Edited 24 Feb 2014 by Mickey

[Ken Roach 194]

Sometimes I think that the MicroLogix user manual editors intentionally tried to keep the analog channel data hard to find. The Analog Output scaling information is in 1766-UM001, under the heading "Latching Inputs", which is about as useful as putting them in a filing cabinet in a disused cellar lavatory behind a sign reading "Beware of the Leopard". Mickey is of course correct; the onboard channels are lower-resolution than the expansion modules.

[daba 4]

Where's the "like" button ? Edited 25 Feb 2014 by daba