Plot Over­view of the Ana­lys­is Soft­ware IfTA TrendView­er

The most im­port­ant plots and groups of plots for visu­al­iz­a­tion

Re­p­res­ents the change of a value over time.

To ana­lyze the exact value of a sig­nal at a time.

Ex­am­ine the change of a sig­nal in cor­rel­a­tion to an­oth­er sig­nal.

The time axes of the plots are auto­mat­ic­ally grouped to­geth­er so that all plots rep­res­ent the same time range, re­gard­less of wheth­er they have an ex­pli­cit or an im­pli­cit time axis. If re­quired, this group­ing can also be changed or dis­solved. In ad­di­tion, the time axis can also be bound to the time curs­or and then rep­res­ents a con­fig­ur­able time win­dow around the time curs­or.

More in­focen­ter top­ics : Ther­moacous­tics | Meas­ure­ment tech­no­logy | Sig­nal pro­cessing

Plots with an Ex­pli­cit Time Axis

Look­ing at the change of a sig­nal over time is one of the most fun­da­ment­al ana­lyses.

IfTA TrendView­er of­fers two plots for this pur­pose:

  1. Trend Plot: Dis­plays scal­ar and Boolean/lo­gic­al sig­nals over time. Even sig­nals with dif­fer­ent time res­ol­u­tion can be dis­played in one plot.
  2. In­tens­ity Plot: Dis­plays spec­tra as spec­tro­gram. In ad­di­tion, sig­nals with the same unit over time can also be dis­played.

Trend Plot

Use the trend plot to ana­lyze value changes over time. The time is plot­ted on the x-axis and the val­ues are plot­ted on the y-axis.

Visu­al­ize how a sig­nal changes over time in trend plots. Find de­pend­en­cies in your data by adding mul­tiple sig­nals to the plot.

Boolean Trend Plot

Use the Trend plot to ana­ly­ze value chan­ges over time. The time is plot­ted on the x-axis and the va­lues are plot­ted on the y-axis.

An­a­ly­ze boo­lean/logic sig­n­als over time and iden­­ti­fy points in time at which chan­ges take place. Sig­n­als are auto­mat­ic­ally stacked and grouped to one y-axis for bet­ter read­­ab­il­ity.

In the ex­­­am­ple run-up and run-down si­g­n­als of a ro­ta­t­ing ma­chi­ne are dis­­­­­played. On the x-axis time is shown and on the y-axis the state (0 for false and 1 for true). As you can see first the ma­chi­ne is in run up state and after a short amount of time it is run down.

 

Wave­form Trend Plot

Use the Trend plot to ana­­lyze value changes over time. The time is plot­ted on the x-axis and the val­ues are plot­ted on the y-axis.

An­a­­lyze wave­­forms to see how the amp­l­itudes and wave­­forms change over time.

The ex­­ample shows a dis­­tance sensor sig­n­al from a ro­tat­ing ma­chine. On the x-axis the time is drawn, on the y-axis the mag­n­itude of the sig­n­al is plot­ted.

Spec­tro­gram Plot

Ana­lyze fre­quency phe­nom­ena over time with a spec­tro­gram. Dis­play amp­litude changes for all fre­quency lines at once.

In the ex­ample the ab­so­lute spec­trum of a pres­sure sensor in­stalled in an acous­tic­ally ex­cited burn­er is dis­played. You can see how the amp­litude of the first har­mon­ic at a fre­quency of ≈175Hz and in­creases and de­creases over time.

On the x-axis the time is dis­played, on the y-axes the spec­trum unit, e.g. fre­quency [Hz]. The color bar on the left defines the col­ors de­pict­ing the mag­nitude of the spec­trum val­ues.

In­ten­si­ty Plot

Dis­­play a group of sig­n­als with the same unit in one in­­tens­ity plot. You get an over­­view of the val­ues over time. Thus, you can quickly identi­fy sensor val­ues which de­vi­ate from the rest of the group and ana­­lyze how val­ues change over time. The plot gives a quick con­­densed over­­view over a group of sig­n­als which is su­per­­i­or in com­­par­is­on to a trend plot.

In the ex­­ample, 24 tur­bine out­­­let tem­per­­at­ures are drawn on the y-axis over the x-axis (time). The tem­per­­at­ure is drawn by color, where the color cor­res­­ponds to a value dis­­­played on the "color bar" on the left side of the plot. 

Plots Visu­al­iz­ing the Val­ues of a Sig­nal at the Pos­i­tion of the Time Curs­or

Look­ing at the change of a sig­nal over time is one of the most fun­da­ment­al ana­lyses. IfTA TrendView­er provides two time curs­ors to ana­lyze the exact value of a sig­nal at a time.

The fol­low­ing plots show the value of sig­nals to the time curs­or:

  • List plot
  • Led plot
  • Spec­trum/Array plot
  • Polar plot

List Plot

Dis­­play the val­ues of sig­n­als at the cur­rent time curs­or po­s­i­­tions. Thus, you can quickly com­­pare val­ues of di­f­fer­­ent sig­n­als and di­f­fer­­ent times.

In the ex­­ample, the cur­rent val­ues of ma­chine state var­i­­ables are shown for time curs­or 1 and 2. Ad­di­­tion­al data is the time, the value di­f­fer­­ence between the two curs­ors and the sig­n­al unit. It is pos­s­ible to con­­fig­ure the num­ber of tables, vis­ible columns and rows.

LED Plot

The LED Plot dis­­­plays states (boolean/lo­­gic­al sig­n­als) at the cur­rent time curs­or po­s­i­­tion. See im­me­di­ately if an error or alarm oc­­curs and if your sys­tem is run­­n­ing cor­rectly.

The ex­­ample shows sev­er­­al bin­ary sig­n­als (green/red for true and grey for false).  A color can be chosen for the act­ive and in­­act­ive state.



Spec­trum Plot

Use the spec­trum plot to ana­­lyze spec­tra for a se­lec­ted point in time. Read the amp­l­itude for all fre­quency lines at once and identi­fy rel­ev­ant fre­quen­­cies at cur­rent time curs­or po­s­i­­tion.

The fig­ure shows the ab­so­lute spec­trum of a pres­sure sensor in­­stalled in an acous­t­ic­ally ex­­­cited burn­er. The res­on­ance peak at 168 Hz is auto­mat­ic­ally marked with a label de­pict­ing the mag­n­itude and fre­quency.

The plot is often used in con­­jun­c­­tion with an in­­tens­ity plot to dis­­­play the val­ues at the cur­rent curs­or point. On the x-axis, the fre­quency is dis­­­played and on the y-axis the mag­n­itude of the spec­trum.



Array Plot

Dis­­­play a group of si­g­n­als with the same unit in one plot. You get an over­­­view of the va­lues at the cur­rent time cur­sor po­si­ti­on. Thus, you can quick­­­ly iden­­ti­fy sen­sor va­lues which de­vi­a­te from the rest of the group.

In the ex­­­am­ple fi­gu­re you can see 24 tur­bi­ne out­­­­­let tem­pe­ra­tu­res. On the x-axis, the sen­sor num­ber is dis­­­­­played and on the y-axis the tem­pe­ra­ture.

Polar Plot

Use the polar plot to gain a quick over­­view over mul­­tiple sig­n­als at once. You can eas­ily see if one sensor provides di­f­fer­­ent data than other sensors for a lar­ger num­ber of meas­ure­­ment sig­n­als.

In the ex­­ample you can see 24 tur­bine out­­­let tem­per­­at­ures drawn equidistantly around the plot ori­­gin.

 

Plots with an im­pli­cit time axis

If the change of a sig­nal is not ob­served over time, but over an­oth­er sig­nal, then plots are used which have an im­pli­cit (not vis­ible in the plot) time axis. This de­term­ines the time peri­od of the val­ues to be dis­played.

The fol­low­ing plots have an im­pli­cit time axis:

  • Bode plot
  • Nyquist plot
  • Orbit plot
  • Shaft Cen­ter­line plot
  • Camp­bell / In­tens­ity map plot
  • XY plot

Bode Plot

Use the Bode plot to ana­ly­ze ma­chi­ne runs. Dis­­­play fre­quen­cy re­spon­ses or har­­­mo­n­ic modes ver­­­sus the ro­ta­­­tio­n­al speed. You will be able to iden­­ti­fy cri­ti­c­al speeds and re­so­n­ances. Eva­lu­a­te angles and ma­g­n­i­tu­des of un­­­ba­lan­ces by ana­ly­z­ing speed, am­pli­tu­des and pha­ses, cal­cu­la­ted in re­fe­rence to a key­pha­sor si­g­n­al. By using ma­chi­ne state co­lo­ring you get a quick over­­­view over a com­ple­te run.

In the ex­­­am­ple fi­gu­re you can see am­pli­tu­de and phase of the first har­­­mo­n­ic mode of a di­stan­ce sen­sor dis­­­­­played over the ro­ta­­­tio­n­al speed in [Hz]. The line color de­pends on the ma­chi­ne state (Here: black: slow roll, blue: run up, green: stea­dy state, red: run down).

In ad­di­ti­on to rotor dy­n­a­m­ics ana­ly­s­is you can dis­­­­­play any com­bi­n­a­ti­on of three si­g­n­als in the Bode plot. Use it to group and dis­­­­­play two time si­g­n­als over a com­­­mon third si­g­n­al.

Nyquist Plot

Identi­fy res­on­ances or crit­ic­al speeds and dis­play har­mon­ic modes with the Nyquist plot. Evalu­ate angles and mag­nitudes of un­bal­ances by ana­lyz­ing speed, amp­litudes and phases, cal­cu­lated in ref­er­ence to a keyphas­or sig­nal. By using ma­chine state col­or­ing you get a quick over­view over a com­plete run.

The ex­ample shows the first har­mon­ic mode of a dis­tance sensor, which meas­ures the dis­tance to a ro­tat­ing shaft. The ima­gin­ary val­ues are plot­ted against the real val­ues while the res­ult­ing points are labeled de­pend­ing on cor­res­pond­ing en­gine speed val­ues.

The point color de­pends on the ma­chine state (here: black: slow roll, blue: run up, green: steady state, red: run down). The com­plex phase (Φ) and amp­litude (r) at the cur­rent curs­or value are writ­ten in the lower right corner. The cur­rent curs­or time is dis­played in the lower left corner.

Orbit Plot

In­vestig­ate shaft vi­bra­tions and un­bal­ances with orbit plots. Visu­al­ize the mo­ment­ary shaft dis­place­ment with re­spect to a sta­tion­ary bear­ing and eval­u­ate the ex­cur­sion of the shaft.
The ex­ample shows the orbit of a ro­torkit shaft de­rived from two or­tho­gon­al dis­place­ment sensors. 
The val­ues of mag­nitude and angle at the cur­rent curs­or po­s­i­tion are shown in the lower right corner. The plot draws two sensor po­s­i­tions cor­res­pond­ing to the x and y sig­nal. Ad­di­tion­ally, the ro­ta­tion dir­ec­tion is shown in the plot by an arrow.

Shaft Cen­ter­line Plot

Mon­it­or sta­tion­ary move­ment of shafts with re­spect to sta­tion­ary bear­ings with shaft center­line plots. Rotor dy­nam­ic ex­perts use this plot to ana­lyze the dis­place­ment of tur­bine or com­pressor shafts moun­ted in hy­draul­ic bear­ings, as the shafts start to float up­wards due to the ro­ta­tion­al move­ment.

In the ex­ample you can see the move­ment of a com­pressor shaft from the lower right corner to the upper left corner.

DC val­ues from dis­place­ment sig­nals are dis­played on the x- and y-axis re­spect­ively. A speed sig­nal can be used for la­beling the data points.

Camp­bell Plot

Draw a spec­trum data source in re­la­tion to a speed sig­nal with the Camp­bell plot. Quickly identi­fy speed de­pend­ent phe­nom­ena and ana­lyze har­mon­ic mode changes.

The ex­ample shows the amp­litude spec­trum of a shaft dis­place­ment sensor over the speed sig­nal of a rotor kit. The first four har­mon­ic modes and how they change in mag­nitude can be seen in the plot (red/yel­low lines).

On the x-axis, the speed is dis­played, the y-axis shows fre­quency in Hz. The mag­nitude of the spec­trum can be de­pic­ted on the ‘col­or bar’ at the left side of the plot. Ad­di­tion­ally, the cur­rent time and range are dis­played in the lower left corner.

In­ten­si­ty Map Plot

Ana­lyze how amp­litudes and fre­quen­cies change de­pend­ing on val­ues of nu­mer­ic sig­nals with the in­tens­ity-map.

In the ex­ample, the ab­so­lute val­ues of a sound spec­trum in de­pend­ence of the mean tur­bine out­let tem­per­at­ure is shown. On the x-axis, the nu­mer­ic sig­nal, the tem­per­at­ure, is dis­played, the y-axis shows the fre­quency in Hz. The color bar on the left defines the col­ors de­pict­ing the mag­nitude of the spec­trum val­ues.

The in­tens­ity-map plots a spec­trum data source over a se­lect­able sig­nal. Ad­di­tion­ally, the time is dis­played in the lower left corner of the plot.

XY Plot

Visu­al­ize sig­nal de­pend­en­cies with the XY-plot, by cor­rel­at­ing sig­nals dir­ectly.

In the ex­ample, the mean tur­bine out­let tem­per­at­ure is plot­ted on the y-axis against the elec­tric power. The cur­rent time po­s­i­tion is shown in the lower left corner of the plot.

The XY plot is used to plot mul­tiple data sources with a shared time re­gion, whereby one data source is plot­ted on the x-axis and all ad­di­tion­al data sources are plot­ted on the y-axis.