Hy "Step-Type Feedback" meaning

[tward]

Does anyone know the purpose of the "Hy" parameter described as "Step-Type Feedback" in menu 0089 of the JLD612? This is not described in the manual.

(Also, Figure 4 of the manual shows this parameter as "Atud" and describes it as "AT Skew Setting". I believe this parameter name and description are incorrect.)

[richiem]

The most recent version of the manual, posted last month, does describe the Hy settings.

[tward]

The most recent version of the manual, posted last month, does describe the Hy settings.

I have the latest version (*). The purpose of "Hy" is implied in Fig. 3 only. It appears that the "Hy" setting is only used whem "outY" = 3 or "outY" = 3. However, it is not clear whether the "HY" in Fig. 3 refers to menu item "Hy", especially since below Fig. 3 the manual states "Note: HY = AH - AL". Since the values of AHx and ALx (x = 1, 2) are set by the user, "HY" is not an independent variable. Thus, the meaning of "Hy" becomes more confusing. The listing of "Atud" "AT Skew Setting" in Fig. 4 creates additional confusion. The manual is not at all clear about the meaning of "Hy".

* From viewtopic.php?f=13&t=3, File comment: New version c1.0 2-15-2011, JLD612_Manual_2011.pdf [441.37 KiB]

[richiem]

I have not used this mode so, YMMV.
Hy lets you set an off-on/on-off deadband of whatever value works for you. The size of Hy is the AH setting minus the AL setting. Initially, at start-up, the reading of the current temp PV has to be less than the set temp SV minus the Hy value. The Hy value lets you control the amount of hysteresis in the system.

Many folks would like to see no hysteresis at all, which is what proportional control tries to deliver and it does in fact work pretty well. But some folks need some deadband in order for their system to work correctly -- this is especially true in industrial control systems of massive size where the various components have very long response times, or are just by nature very noisy or unpredictable due to fluid or gas flow characteristics or other physical disturbances that tend to be chaotic -- like the chaotic mixing of cooler and warmer water is a sous-vide pot during heating, for example.

Folks like us really are not the main customer base for these units, and I think our expectations can be a bit higher than the gear sometimes can deliver. If I could read Chinese, and if I were expert in industrial control systems, then none of the problems I've had in the past would have been problems, they just would have been normal burps on the way to successful applications of technology that I completely understand.......

[tward]

I have not used this mode so, YMMV.
Hy lets you set an off-on/on-off deadband of whatever value works for you. The size of Hy is the AH setting minus the AL setting. Initially, at start-up, the reading of the current temp PV has to be less than the set temp SV minus the Hy value. The Hy value lets you control the amount of hysteresis in the system. ...

I guess YMMV = "Your Method May Vary"?

Anyway, I understand the concepts of deadband and hysteresis. It's just that I can't understand how I can set an independent variable that also is defined as the difference of two other user-defined independent variables, AH and AL. If Hy = AH - AL and I set the values for AH and AL, how can I also set the value for Hy?

I get a bit more confused because the system actually has two AH-AL pairs, AH1-AL1 and AH2-AL2. Also, the Hy variable is set in the 0089 menu while the AH and AL variables are set in the 0001 menu.

So even though I understand the concepts, I cannot understand what the manual seems to be trying to say. I think it's a combination of incomplete descriptions, English language issues (in the manual), and some contradictions within the manual (such as "Hy" in the table" and "Atud" in the diagram).

[richiem]

Yeah, good point about setting an independent Hy value -- I guess I was reading too fast and thinking too little.... Now I'm confused too. It's time to hear from Marco....

[Tech_Marco]

HY sounds like an absolute value.

Example1 (heating): SV = 100'C, HY =3'C
When temp dropped to 97'C, the relay take action and latched to start heat up process

Example2 (cooling): SV = 28'C and HY =2'C
When temperature rise up to 30'C, the relay latched and cooling process started

Clear?