temprature increase per min

hello all
here is a application...i have to increase temperature of a furnace. furnace heater works on 4-20 mA 0 -1500 deg.
now i have to increase temp. 5 deg./min.
any body can tell me how to do this.

Use a 1 Minute Timer that increments the heating SP by 5° every time it completes, then resets it self until the actual temp = sp.

Thanks Janner

yes i can increase SP by using timer......
should i use a pid for this?

Does the furnace take a 4mA - 20mA signal to set its temperature?

yes

application is

Room temp. to 500 in 2 hrs
500 to 1000 in 4 hrs
1000 to 1300 in 2 hrs
1300 to 1500 in 2 hrs

1500 to 1000 in 3 hrs


like this

Here's a quick sample.

It will increase the Temp SP by 5°C every 1 minute.

It then scales to a 4 - 20mA output. You will have to adapt the code for when it gets to 1500 °C to turn it off the timer and hold the SP at 1500 °C

You will need to change your scaling if your analogue card uses a different range.

thanks

but we have to monitor TT value that temp increasing is 5 deg/min or less or greater than
5. in case that is not ok then how to control that

Are you doing a curing process for a fresh install or is this the actual process?

Calculate rate of change for temperature, alarm if out of range.

Run a trim loop against the ROC for temp, trim the output of your primary control based on that.

its a actual process

thanks dravik

Date Time TT_31.PV
7/19/2017 7:24:00 PM 1,289.23
7/19/2017 7:18:00 PM 1,317.76
7/19/2017 7:12:00 PM 1,344.13
7/19/2017 7:06:00 PM 1,367.01
7/19/2017 7:00:00 PM 1,393.97
7/19/2017 6:54:00 PM 1,418.20
7/19/2017 6:48:00 PM 1,443.97
7/19/2017 6:42:00 PM 1,472.52
7/19/2017 6:36:00 PM 1,495.40
7/19/2017 6:30:00 PM 1,493.69
7/19/2017 6:24:00 PM 1,480.25
7/19/2017 6:18:00 PM 1,464.87
7/19/2017 6:12:00 PM 1,449.06
7/19/2017 6:06:00 PM 1,432.87
7/19/2017 6:00:00 PM 1,416.19
7/19/2017 5:54:00 PM 1,397.80
7/19/2017 5:48:00 PM 1,376.97
7/19/2017 5:42:00 PM 1,355.25
7/19/2017 5:36:00 PM 1,336.53
7/19/2017 5:30:00 PM 1,315.95
7/19/2017 5:24:00 PM 1,301.39
7/19/2017 5:18:00 PM 1,288.41
7/19/2017 5:12:00 PM 1,274.86
7/19/2017 5:06:00 PM 1,260.68
7/19/2017 5:00:00 PM 1,246.54
7/19/2017 4:54:00 PM 1,231.86
7/19/2017 4:48:00 PM 1,216.74
7/19/2017 4:42:00 PM 1,200.49
7/19/2017 4:36:00 PM 1,182.44
7/19/2017 4:30:00 PM 1,167.70
7/19/2017 4:24:00 PM 1,152.65
7/19/2017 4:18:00 PM 1,136.45
7/19/2017 4:12:00 PM 1,118.94
7/19/2017 4:06:00 PM 1,100.95
7/19/2017 4:00:00 PM 1,084.16
7/19/2017 3:54:00 PM 1,069.04
7/19/2017 3:48:00 PM 1,051.32
7/19/2017 3:42:00 PM 1,033.54
7/19/2017 3:36:00 PM 1,016.99
7/19/2017 3:30:00 PM 1,017.79

Time TT_31.PV TT_32.PV
7:24:00 PM 1,289.23 1,272.82
7:18:00 PM 1,317.76 1,298.24
7:12:00 PM 1,344.13 1,324.53
7:06:00 PM 1,367.01 1,350.55
7:00:00 PM 1,393.97 1,376.97
6:54:00 PM 1,418.20 1,402.19
6:48:00 PM 1,443.97 1,429.03
6:42:00 PM 1,472.52 1,455.96
6:36:00 PM 1,495.40 1,483.16
6:30:00 PM 1,493.69 1,506.82
6:24:00 PM 1,480.25 1,504.32
6:18:00 PM 1,464.87 1,483.98
6:12:00 PM 1,449.06 1,464.25
6:06:00 PM 1,432.87 1,443.98
6:00:00 PM 1,416.19 1,424.76
5:54:00 PM 1,397.80 1,405.02
5:48:00 PM 1,376.97 1,385.35
5:42:00 PM 1,355.25 1,365.31
5:36:00 PM 1,336.53 1,346.18
5:30:00 PM 1,315.95 1,325.97
5:24:00 PM 1,301.39 1,307.52
5:18:00 PM 1,288.41 1,291.02
5:12:00 PM 1,274.86 1,275.00
5:06:00 PM 1,260.68 1,258.78
5:00:00 PM 1,246.54 1,241.60
4:54:00 PM 1,231.86 1,225.05
4:48:00 PM 1,216.74 1,208.51
4:42:00 PM 1,200.49 1,192.38
4:36:00 PM 1,182.44 1,175.78
4:30:00 PM 1,167.70 1,159.30
4:24:00 PM 1,152.65 1,142.58
4:18:00 PM 1,136.45 1,125.83
4:12:00 PM 1,118.94 1,109.50
4:06:00 PM 1,100.95 1,092.39
4:00:00 PM 1,084.16 1,074.90
3:54:00 PM 1,069.04 1,058.57
3:48:00 PM 1,051.32 1,042.44
3:42:00 PM 1,033.54 1,024.69
3:36:00 PM 1,016.99 1,008.85
3:30:00 PM 1,017.79 994.17

I would not increase every minute, but increase every cycle (assuming you know the cycle time). We work with 100 ms cycles, in that case you would increase sp by 5/600 degrees/cycle.

you could then look at the difference between sp and pv.