INSTR UC TI ON MANUAL F OR TH E S E N CORE FE1 4 & F E16
Th e S e n c o re FE14 and F E 16 F ie l d E f fe ct M et e r s are a rev o lution a r y new co n ce pt
in te s t m e t ers. The y take all the a dv an tag es of a V TV M and c o m b i n e them with
the ad va nt ag es of a VOM to m ak e an e xtre mely versatile me t er. High input i m
ped an c e on all AC & DC v olt ag e r a n g e s , pe ak to pe a k AC me asurem e nts, & DC
zero center sc ale s com bi ne d with z e r o wa rm up ti m e , DC c u rrent r a n g e s , and
VOM p o rt a b i li ty m a k e s the Fi e l d E f f e c t Mete r a tru l y great inst r u ment . Anyone
in the el ect r i cal o r el ectr onic field s - s erv i c e t e c h nicia n s , engin e ers, fiel d eng
in eers , ha m s , e x peri men t e r s e t c . - wi ll find that the Fi e l d Effec t M et e r is the
co m p l e te an s w e r to h is measu r i n g needs.
No othe r mete r in the F E14 o r FE1 6 cl ass has a l l of the s e fe atur e s in one ins tr u ment:
* High input imped an ce on both AC and DC v o lta g e ra nges (1 0 m e g oh m s ,
and 15 megohm)
* T r ue p e ak to pe a k AC ran g e s .
* Z ero ce nter r a nges fo r s olid s ta te s e r v i c ing.
* DC cu r r ent ran ges fo r genera l test in g.
* M i r r ored scal e mete r fo r great e r a c c ura c y in readings .
* Mete r pro te c t e d fro m o v e r lo a d s .
* C i r c uit p r o te c te d fr o m ac c id e n t a l app li ca ti on of w ron g vo l ta g e s.
* All s t e e l con s t r u c ti o n for g r eate r du ra bi lit y .
FI ELD E FFE CT METE RS
* B at te r y op er at ed fo r complet e por ta b ili ty .
FE14 S PE CI FI CA T IO N S
DC VOL T S
Ra nges : 0 to 1, 3, 10, 30, 10 0, 300 and 1000 FULL SC A L E
Input Res i s t a nce : 1 5 meg o hm s shunted by 14 PF .
A c c u r a c y : + 2 1/2% »
AC R eject i o n: 3 0 to 300 times (3 0 to 50db).
AC VO L T S
Ra nges : ( R m s )
Ra nges : ( P eak to Peak)
Input Resi s t anc e : 10 me g oh m s shunted by 29 PF .
Fr e quen c y Re s p o n s e : Flat : 25HZ to 1MHZ
A cc urac y : + 4 1/2%
- .5 to .5 , - 1.5 to 1 . 5, -5 to 5, -1 5 to 15 , -50 to 50, -150 to 15 0
and -500 to 5 0 0 ZE R O C E NTER S CAL E RAN G ES
0 to 1, 3, 10 , 30, 10 0, 3 00 and 1 0 00 FULL SC A L E
0 -2 . 8, 8.4, 28, 84 , 2 80, 840 and 28 0 0 F ull Sc a l e , fr e q ue n cy
com p e n sa te d
3db po i nt s : 10Hz to 10MHz
OHMM E T E R
Rang e s : 0 to 1000 o h m s , 10K , LOOK, 10 me g o h m s and 1000 mego h m s
A c c u r acy: + 2 de g rees AR C
DC CU RRE NT MEAS U REME NTS
Ra nges: 0 - 10 0 m icroa mps , I ma, lOma, lOOma and 1 A m p e re
A c c u r a c y: + 3%
In te r n a l Vo l ta g e D rop : 200 MV
F E16 SPE C IF IC A T IO N S
DC V O L T S
Ra nge s : 0 to 1, 3, 10 , 30, 10 0, 300 and 1000 FULL S C ALE
Input Res i sta nce : 15 meg o h m s shunted by 14 PF a t jack or 37 PF th ru cable
A c c u r a c y: + 1.5 %
AC Rejec t i on: 30 to 300 t i mes (3 0 to 50db),
AC VO L TS
R a n ges: (Rms )
R a n ges: (P ea k to Peak )
Input Resistance : 10 meg o hm s shunted by 29 P F at ja ck or 118 P F thru ca ble
Fr e quency R e s p onse : F l at: 25H Z to 1MHZ
A c c u r a c y: + 3%
OH MME T E R
Ra nges : 0 to 10 00 oh m s , 10K, 10 0K , 10 me g oh m s and 1000 mego hm s
A c c urac y : + 2 d egre e s ARC
5 to . 5, -1. 5 to 1. 5, - 5 to 5, - 15 to 15, - 50 to 50, -150 to 150
and -500 to 500 ZE RO CE NTER SC A L E R A NG E S
0 to 1, 3, 10, 3 0 , 1 00 , 3 0 0 and 1000 FU LL SC ALE
0-2 .8 , 8 .4, 28, 84, 2 80 , 84 0 and 2800 F ull s cale, fre q u e n cy
compen s at e d
3db p o in t s : 10H z to 10MHz
DC CU RRE NT MEAS U REME NTS
Ra n g e s : 0 - 10 0 micr o amp s , I m a, lOma , lOOma and 1 A m p er e
A c c u r a c y: + 3% fu ll s c ale
Int e r n al V o lt ag e D ro p : 2 00 M V
G E NERAL SP E C IF I C A T IO NS ON FE14 AND FE 1 6
Meter: 4 - 1/2 ", 10 0 micr o a m p + 2%, diode p r otec te d and is o l a te d fr o m input
M u l t iplier Resis tors: 1% prec i sion type on F E14; 1/2% on FE16
Oh m s B a t tery: 1. 5V "C" c e l l , Evere a dy Type # 10 35 o r e qu i v al en t
Powe r supply ba t t e r y : 9 volt, E v e r e ady Type #222 or eq u i va le n t
Weight ( l ess Batt eries): 3- 1 / 4 lb s .
Di mens i o ns: 5 " w x 7-3/16 ”h 3 - l/l 6d
Acces sorie s: High Vo l ta g e pro b e (3 9 A19 ) ext en d s ra nge to 30K V.
CO N T R OLS ON THE F E14 & FE16
The Fi e l d Eff ect M e t er is a s s i m p l e to ope r a te a s a s t an d a r d VOM. P an el c o ntro ls
inc lud e the RAN GE swit c h, FU NC TI ON sw itch , met er ZERO ADJ, OHMS AD], and
the of f - o n switch. T h e follow in g is a b r i e f d e s c r iption o f ea c h c o n t r o l and how it
is used.
O FF-ON sw itc h : T h e OFF -ON switch co n t r ols the pow er to the circu i t in the Fi e l d
E f f e ct Me t e r . In the OFF posit io n, the ba t t e ry i s di sc o n n e c te d fro m the ci r cuit
and the me t er is off. In the ON position , the ba t t e r y v olt ag e is applied to the cir cuit
and the m e t e r i s re a dy to g o. A r ed fla g ap p e a r s in the swi tc h openi ng to indi ca te
when the Fie ld Effect Mete r i s on. When m easu r i n g cu r r e nt, the OFF-ON s wit ch
ma y be left in the O FF pos it io n as no b a t te r y powe r i s need ed.
ZERO ADJ: T he ZE RO ADJ i s used to p o si ti o n the po in t e r of the met e r o v e r the
zero on the ex t r e me l ef t of the meter s cale o r to p o si ti on the po i nt e r on the cen te r
zero when us ing the ze r o ce nter ran ges of the Field E f f e c t Meter.
OHMS ADJ: Th e OHMS ADJ i s the sam e a s that found on mo s t m ete r s . P r ior to
m e a s u r i n g r e sist a nce , the tes t le a ds a r e sh o rt e d tog et h er and the OHMS ADJ is
ro ta t e d f o r a full s c ale defl ec ti o n (z e ro o h ms) as rea d on the ohms s cale o f the
m e t er.
FUNC TIO N SWIT CH: Th e FUN CTION sw itc h se lec t s the type of meas u r e ment to be
pr e f o r med. Min us o r Plus DC Volts or MA, AC vo lts o r OHMS and the BAT T . CHK.
RANGE S WITC H: The RANGE switc h select s the d e s i r e d ran g e of cu r r e nt, voltag e,
or r esistance to be me as u r ed .
SH I E L D E D LE A D ON T H E FE1 4 & FE16
Th e Sen c o r e Fi e ld Effe ct Meters ar e equipped with a shiel d ed lea d cm .the po s it iv e
input lead so that a c cura t e AC me asur e men ts ca n be made in the presen c e of
str o ng elec t rost atic and m a gn e ti c fiel d s . T h e s hi el d, which i s a l s o ef fectiv e on
high ohms ranges , is only con ne ct ed when u s in g the AC Volts / O hms fu n ct io n s and
is d is c on n ec t ed when mak ing DC meas uremen ts to p re v e nt capac i t ive loading of
the circu i t being mea s u r e d .
T est l ea d co n ne c ti o ns to the F E14 or F E16 a r e made through the re d and b la c k
bana na jacks . T h e shi el d c o n n ec t s through a s mall pin j ack ( p la in ly ma rk e d) so
that it cannot be m i s t a k e n l y used a s one of the te s t lead co n n e c ti o n s .
OPE RA T IN G THE FE14 and F E 1 6
The Senc o r e Fi e ld Effe c t M e t e r s a r e s i m p l e and ea s y to o perat e . Set the Fu nc t io n
swi tch to the d e s i re d t e st to be pref o rmed, the RA NG E switc h to the de s i r e d rang e ,
co n n e ct the lead s and r e a d the re s ults on the me t er. H er e is a b r i e f de s c r i p t ion of
how eac h te s t is pe r fo r med.
READ IN G DC VOL T S : To rea d DC v olt s, th e F u nc t io n sw i tch is se t to eith e r plus
or m inu s DCV/MA. T he Ra ng e sw itch is set to the des i re d r a n g e of volt ag e f r o m
one volt' to 1000 volt s full scal e . If the volta g e to be me a s u r e d i s unknown, st art
with the hi gh e st ran ge and w ork down until t he vol ta ge can be m e a s u r e d. Co nn ect
the le ad s to the c ircu i t and rea d the re s ults on the m e t er. When measur i n g voltag e
in R F-IF ci r c uits , a 10 0 K iso l a ti on r esi sto r at the end of the re d te s t le a d will
re d uce cap a c it i ve e f f e c t s without e ff e ct i n g a c cur a cy of r e a d i n g s .
The DC vo ltage i s re a d on the two blac k s cales ju st above the mir ror on the me t e r .
Th e top DC sca l e i s fro m zero to 1 . 0 volts and e a ch mark is e qu a l to .02 vo lt s.
Th e b o t to m sc a l e is zero to 3. 0 volts and eac h marki s e qu al to . 1 v o lt s. Th e z e ro
to 1 . 0 sc ale is us e dfor the 1, 10, 10 0, and 10 0 0 volt r a n g e s and the ze r o to 3 . 0
sc ale i s used for the 3, 30, and 3 00 volt r ang e s . In use the m e t e r in di ca ti o n is
mu lti pl ie d by 10, 100, o r 100 0 depending upon the ra n g e . For exa m p l e , i f the
ra nge sw i tc h is on the 10 volt ran g e and the meter reads . 42 vo lts , the actu a l v o l
tag e i s . 4 2 t i mes 10 or 4. 2 volts DC.
RE A D IN G AC VO L T S : To read AC vol ts , the Fu n c t io n s w it c h i s s e t to the ACV/OHMS
po si ti o n and the Rang e sw it ch to the desi r e d r a n ge. For RM S volt ag e s the two
bl a c k s cal es mar k e d AC (RMS) a r e used. For pea k to peak vo lta g es , the two red
s c ale s dire c t l y be low the AC (RMS ) scale s are u se d. The rea d i n g s a r e multip li ed
in the same way a s with the DC s cal es, to obtai n the ac t u a l voltage pres e nt. On
the z e r o to 1 .0 AC (RMS ) scal e, each mark is . 02 vo l ts and on the zer o to 3. 0 vo lts
scale, ea ch mar k is . 1 vo l ts . On the ze r o to 2. 8 vo lt s AC (P-P) s c a l e , ea c h mark
is . 1 v olt s and on the zero to 8. 4 vol ts sc a l e, each mar k i s . 2 vo lts .
REA D IN G DC VO L T S ZERO CE NTE R SC ALE: T h e z e r o ce nter s cales a r e used to
re ad plu s or min us vol ta g es without the necessit y of c ha ng in g pola r i ty with the
le a d s or Fun c tio n s w itc h. To us e the ze r o c e n t er s cal es, set the Func tio n switc h
to plus DCV/M A p o s it io n and adj u s t the ZER O ADJ until the meter r e a ds at the
z e ro m a r k in the cent e r of the s c ale . This gi v es r a n ges o f plus or min us . 5 volt s
(top sca l e) or pl us or minu s 1. 5 vo l ts (botto m sc a l e) ti mes 10, 10 0, o r 100 0 de
pending upon the se tt in g of the r a n ge swi tc h . If the ran g e swit ch is in the 300 volt
po si ti o n , the zero to 1. 5 vol ts sc ale i s us ed and bec ome s zer o to 150 volt s pl us or
mi n u s. If the meter swin g s up sc ale or to the righ t , it is a po si ti ve volta ge . If
the mete r swings down scal e or to the le f t , i t is a n eg e ti v e vol ta ge . Th i s unique
fe a t u r e a ll o w s you to det e r mine th e po l a r i t y as w el l a s the am p litu de of a DC vol
tag e and i s ve r y handy in so li d st a t e serv i c i n g .
REA D IN G OHMS: To re a d resi s t ance, se t the Fun c ti o n sw it c h to ACV/OHMS and
the Ran g e swit ch to the des i r e d ra n g e of resi s t ance to be read. Aft er c h e c k in g to
see that the meter i s "zeroed " at the le f t edge of the s c ale, short the lea ds to g e th e r
and ad j us t the OHMS ADJ con t r o l for fu ll s c ale de fl e c t ion o f the m e t e r . U ns h or t
the le a d s and be sur e tha t the m eter r etur ns to the ex t r e m e l e ft of the scale. Plac e
the unknown r esistance b et we en the two lead s and r e a d the resist anc e on the Gil VIS
scale (top re d s cale on m e t er). Mu lt ip ly the rea d i n g on the meter by the ran ge
use d. For ex a mple, if the m eter r e a d 15 and the ran g e switc h was s et on RX1 0 0 ,
the ac tu a l resista nce would be 15 times 1 00 or 1 5 0 0 oh ms. CAUTION : When mak
ing o h m s m easu r eme n t s , be su r e t ha t the p o we r to the c i rcuit is tur ned off . The
ap p li ca t io n of e xce s siv e vol t ages to the RX 1 , R X10, and RX100 ohm s r a nges ca n
da m a ge the i n t e r n a l s tan d ar d r esist or of the Fi e l d E f fect Mete r .
MEA SU R IN G DC CURR E N T: To mea sure DC cu r r ent, the Fu nc tio n s wit ch is s e t
to eit h er the plus or minu s DCV/MA pos it io n and the Ra n g e switch to the d e s i r e d
ra nge of c urre nt. Th e powe r to the F ield E f fect M e t e r d o e s not have to be turned
on and may be l e ft off to co n s erve on ba t te r y li f e if you s o desi r e. C o nn e ct the
le a d s in serie s and re ad the r e s ulta n t c urre nt on the met e r . The 0 to 1.0 DC
VOLT S (MA) scale is u se d o n all curr e nt me a surements . If the met e r r e ads b a ck
wa r d s , in d ica t in g that the lea d s are r eve r s ed, simply chan g e the p olari ty with the
Fu n c t io n sw itc h to the op p os it e polari t y and the m eter will read up sc ale.
MEA S UR IN G HIGH V O L TA G E WITH THE F E14 AND FE 16
CAU TI ON : High voltag e i s dan g er o u s and c a ut i on should be ob se r v e d when m e a-
su r i n g high volt ages. Be su r e tha t the ground lead fr o m the Fi e l d E f f ect Me t ei is
co n n e ct e d to the ground on the unit. If the ground lea d is not co n n ec te d , you θ ί β
mer ely exten di ng the high v o lta ge c l oser to you. Stand away fro m the unit you a r e
m e a s urin g and keep o ne hand in your po ck e t a s a sa f e t y measur e . High volta g e (Π
color TV is e s peci a l l y da ng e ro u s be c a use it can go a s high as 30, 00 0 vo l ts and
re g u l a t e d . If you should co m e acr oss it, it will not load down.
IS
The 39A 19 High V ol tag e Prob e is an option al asse s sor y, used to e xt en d the DC
range of the Fi e ld Effe ct Mete r to 30, 0 0 0 vo lts . It c o n ta i n s a 1, 485 mego h m 2%
resist or to give a 100 X mul ti p li e r fo r any r a n g e o f the F i e l d E ffect Me t e r. Th e
sp e c i a l r a n g e s of 3KV for bo os t v o lta g es , 10K V for focu s and 30KV f o r high vol
tage a re mar k ed righ t on the f ro nt pan el . Do not me a s u re v oltag e s high e r than
30KV with the 39A19 high voltag e probe , as the ma x im u m rat i ng of the resi s tor
is 30KV.
To us e the High Vo lt ag e Probe , s im p l y plug the test lead into the red jack of the
Fi e ld Effect Me t e r and conn ec t the bla ck l ead fr o m the b la c k ja ck to gr oun d. Set
the f un cti on switc h to + DCV/MA (-D CV / MA if you are m easu r i n g a neg a tiv e vol
tage) and the r a ng e s wit ch to the 3KV, 10KV , o r 3 0 K V p o si ti o n dependin g upon the
volt ag e to be meas u re d .
To re a d the a c tu al vo lta ge, m ulti ply the rea d i n g s on the 3 volt sca l e by 10 0 0 f o r
the 3ICV pos it io n, the 1 volt s c ale by 10, 0 0 0 fo r the 10K V posi ti o n, and the 3 volt
sc ale by 10, 0 00 for the 30 K V p osit io n.
Th e High V ol ta ge Pr ob e ca n al s o be used to me a s ure vo l ta g e s of 1 00 , 300 , and 1000
vol ts DC with an input impeda nce of 1, 500 m eg o h m s . T o obtai n th is high input i m
ped anc e, set the r a n ge switch to the 1, 3, or 1 0 vo lt ran g e and me asur e the voltag e
using the 39A19 High Voltag e P robe .
CHECK ING THE B ATTERIE S OF TH E FE14 AND FE 1 6
The 9 volt trans i s t o r ba tt e r y used in the F ield E f f e c t Me t e r c a n re a dily be ch e c k
ed using the B A T T . CHK. posit io n of the Fu nc t io n sw it ch . T h e r a n g e swi tc h may
be in any posit io n and w ill not eff e c t the r e a d in g of the ba tt e r y cond it io n. If the
m eter re a d s in the g re e n a rea or BAT T GOOD s e c ti o n o f the mete r ( l o wer rig ht
hand c o r n er) the ba tt e r y i s good and the rea ding s tak en with the F i e l d Effe ct Met er
will be accu r ate. If the m e t e r re a d s below the g r e e n ar e a, the b a t t e r y should be
re p la c e d . The ohm s bat t e ry can also be chec k e d ea sily by using the sa me s c a l e
on the Fie l d Ef f e c t M e t e r . Set the s witc h to A C V -O H M S and the Ran ge switch to
RxlO . Adju st the me t e r f o r zer o ind ic ati on on the lef t edge of the scale with the
ZE RO ADJ c o n t ro l . Sho r t the leads to g e th e r and se t the OHMS ADJ for ful l s c a l e
m e t e r ind ic atio n . Without un sh or tin g the lead s , sw itc h the RANGE swi tc h to R X 1 .
If the m e t e r reads in the gre e n ar e a or B A T T GOOD (l o w e r r ight hand c o r ner) the
ohm s ba t t e ry i s good. If it rea ds below this, the ohm s b a t t e r y shou ld be re p l a ce d.
MEAS URIN G HIGH DC CUR R E NT
Up to 10 amps of DC curr ent c a n be me a s u r e d with the Fie l d E f f ect Meter a da pto r
below. U se a double 3/4 i nch banana pl ug and two f e et o f num b e r 20 cop p e r w ir e
to form the shunt. The lea ds c a r r y i n g the >current to the shunt should be a number
14 or hea v i e r with he avy clips to co n n ec t into the circui t .
To us e the 10 amp ada p to r, plug it int o the jack s on the Fi e ld Eff e c t Mete r . Se t
the ra n g e sw it ch to the 10 0 mic roam p po s iti o n and the Fu n ct io n sw itc h to plu s
D CV/ MA. T h e Fiel d Effect M e t e r do e s not need to be turn ed on for curre nt mea sur e
me n t s . Mul ti pl y the re a d ings on the 0 - 1 DC volt s sc ale by 10 to g et the cur r e nt
in am p s . If the meter r e ads bac k w a rd s , r evers e the polari t y by s w itc h in g the
min u s DCV/ MA p o si ti o n.
Double 3 / 4 " Banana plug M fg. Mfg. part number
E. F . John so n
G e n e r al Radio
Natio na l
Pomon a
ME AS U RI NG AC CU R R ENT WITH TH E FE14 AND FE16
Th e F i e l d Effe ct Me t e r ca n be used to m e a s ure AC cu r r ent with the cir cui t shown
below . Th e resist or o r r esi stor s are plac ed in s eri es with the AC so urce going
to th e d e v i ce u nder t e s t . Th e AC volta ge drop acro ss the resi sto r is meas u r e d
and c a n be c o n v e r t e d di rect ly into AC amp s . Th i s ad ap to r ma y be built in a box
with a switc h to fa cilit ate the swi tc hi ng . Th e resis tors use d a r e a l l one o hm of at
le astone wat t. T h e Oh m it e 99 5 serie s of 1 1/2 watt wirew oun d a r e id ea l f o r t h i s.
A standa rd one wat t ca r b o n r es i stor wi ll al s o work . If the unit is to be us e d for
an extend ed perio d of t im e and is e n c lo s e d in a b ox, it is a good i dea to use a two
watt ca r b o n in p l ace of the one watt car b o n r esi s tor .
Type 108
2 74-MB
FWT
MDP-A MDP -
ST
FIG URE 2
When meas urin g f r o m zero to one am p, the one ohm r esist or is used and the
Fun ct io n swi tc h is se t on ACV/OHMS and the Range s w itch to the one volt p o s it io n .
To meas ure t h r ee amp s of AC cu r r e nt, th r e e resi stors a r e p la c e d in p a r alle l . T h e
Ran ge s w it ch re m a i n s on the one volt ran g e , but the thr e e vo lt scal e is re a d d i r e ctly
in a m ps. A 10 amp ra n g e c a n al s o be made by pa ra l l e l i n g 10 one ohm resis tors
and using the one volt scal e, mu l tip ly your re a d in g s by 10.
Very sm all cu r r e nts n an oam ps (. 0 01 ua) may be meas ured usi n g Che Fie ld Eff e c t
M e t e r in conju n ct io n with a 3 volt batt e ry .
Le a k a g e curre nts of tr ans i s t ors and dio de s and lea k ag e cur r e nts th rou gh pap e r or
el ectr olyt i c cap a c i t ors ca n be mea s u re d .
To m a ke nan oam ps m e a s urement s s e t the Fun c t io n Switc h to + D CV / m a and Range
Switch to 3 vo lts . Con n e ct the 3 volt ba t te r y a cross the input term ina l s ; m e t e r
should rea d full s c ale or slig h tl y hig h er . Co n ne c t tr ans i s t or diode or cap a c i t o r
betw e en one batt e r y ter mina l and the Field Effe c t Mete r input. Obser v e p o l a ri t y
when c o n ne c ti ng to devi ce to o bta in an ac c u rate ind ic a ti on . Re a d current on ma
scale and multip ly re a d in g by 200. Cu r re n t m easu r e d w i ll be in nanoa m ps . For
ex ample;
a germ a n iu m diode lea k ag e in dic at io n is . 98 m a . . 98 x 200 = 196 n anoa mp s
a si li c o n diode le ak a g e indi ca tio n is . 1 ma. . 1 x 200 = 2 0 na no am ps
OV E R L O A D PROT EC T IO N ON T H E FE14 AND F E16
The c i r cui t s and me t er o f the F ie l d E f f e c t Met ers a r e protected fro m acc id e n t a l
ov e rl o a d s and applic at io n o f ex cessive v o lt a g e s . A sil i c o n d iode p r otects the t r a n
s i s tor s and circ uit fro m dam a g e. The mete r is p r otec t e d by two d io d e s and a re
si sto r . Th e diod es shunt e x cessive c urre n t arou nd the m e t er. If the cu r rent is
exce s s i vly high or is ap plied for too lon g a p e r i o d of t ime, the fu se res i stor R24
will burn out pr o t ec t i n g the m e t e r and diod e s. When th is r esi stor is open, the
curre nt and o hm s func tion o f the F ield Ef f e c t M eters will be ino p e r a t iv e , but the
m e t er c a n st i l l be used to m e a s u r e v olta ge . R2 4 i s a s ta n d ar d 1 0 0 ohm , 1/2 watt,
10% resi s t or, lo ca t ed on the Rang e switc h, and is re a dily acc ess abl e when the
m e t er is rem ov e d fro m the case.
DISA SS E MB L Y IN ST RUC TI ON S
Th e F i e l d Ef fect Me ter d oe s not have to be take n apart to r eplace the b atte r i e s .
Th e doo r on the bac k o f the F i e l d Eff e c t Mete r g ives a ccess to the batte r i es and
ba t t e r y clip s f o r ea s e of rep la c e ment . If the Fiel d Eff e ct Me t e r must be ser v i c e d
or c a l i b r a t e d , the b at t e ry door m us t fi rst be rem o v e d . T h e n the two screws hold
ing the fro n t panel to the c ase ar e rem o ve d . This allo w s the fro n t p a n el to be
lift ed out fo r s ervi ce. To s e parat e the fron t pane l fr om the case , the b a t t e r y d oor
with the bat t e ries m us t be p a s s e d through the hole in the b a c k o f the case .
BATTERY R E P LACE MEN T : T o r e p l a c e the ba t t eries in the Fi e l d E f f ect Me t e r,
re move the sc r e w holding the b a t te r y plate in the b a c k of the ins t r u ment . T he
batte r y p la te will sl ip out e xp o si ng the bat t erie s i n the cli ps on the p l a t e .
The 9 volt b a t t e ry can be r e p l a c e d by any stan d ar d 9 volt t ran sistor b a t t e r y . An
Ev e r e a d y type #222 or eq ui ve le nt i s rec o mmen d e d as i t w il l giv e l o n g e r ba tt e r y
lif e . The 1. 5 volt "C ” cell ca n be repl a ce d by an y st an d ar d "C " cel l . One of the
man y long l if e t yp es will provid e longe r li fe in us e . T o co nser ve on bat t e r y life ,
the Fi e l d E f f e ct Me t e r should be turned o ff when not in us e or when m e a su r i n g
cu r rent . The 9 volt batt e ry is us ed only when the Fi e l d Effect Mete r i s measu r i n g
AC and DC v olts and r esis tan c e.
The Fi e l d Ef f e ct Mete r m a y be recal i brat ed e a sily and qui c kl y if it beco mes ne
c essary by si mply r emovi n g the batte r y plat e. This will ex p o s e the c ont r ols on
the prin t e d bo a rd . Figu r e t h r e e sh ow s the loc a ti on of th e s e controls . T h e 9 volt
ba t t e r y sh ou ld be re p l a c ed with afr esh one if the Fi e l d Effe ct Me t e r i s to be co m
pl e t e l y re cali bra t ed. Th e DC BAL and the meter mechani c al zer o mu st be chec k
ed and readjus t e d i f n ece ssa r y b e f o r e re cali b r atin g the unit.
1. Se t the fro n t pa n el ZE R O ADJ to the mech a n i c a l ce nte r of it s ro ta t i o n , the
Ran g e s w it c h to the 1 0 00 volt p o s it io n , and tu rn the F ield Effe ct Met e r on.
2. With the F u n c ti o n sw it ch in the plus DCV/MA po s it io n , ad j u s t the DC BAL for
a ze r o m e t e r i n d ic at io n . S witc h to minu s DCV/MA. If the meter po in te r m o v e s,
rechec k and r eset the meter mech anic a l ze ro with the Fi e l d E f f e ct Mete r turned
off . R ech e ck the DC B AL fo r a z e r o met e r in d ica ti on .
3. Se t the R a n ge sw i tch to the 1 volt posit ion and the Fu n c t io n s w itc h to ACV/OHMS.
Apply a known 1 volt AC RMS vo lta g e and a d ju st the AC C A L f o r fu ll sc ale meter
de f le c t i o n . R e move y o u r hand from the AC CA L pot to be s u r e you ar e not pi ck i n g
up any s t ray AC and adding it to the cali b r a t ion o f the F i e l d E f f ect Met e r . If an
accu r a t e so urce o f AC is nota v ailab l e , the AC li n e may b e used. In this cas e , s e t
the R a n ge swi tc h to the 300 vo lt p o sit io n and adj u st the AC CAL co n t r o l to rea d
the lin e vol ta g e . Th i s wil l no rmall y be 115 to 1 17 volt s.
FIG U R E 3
4. EX] c alib r atio n i s ac h iv ed by sett in g the Fun ct io n sw it c h to pl us DCV /MA d
the Ran g e sw it ch to the 1 vo l tp ositio n. Apply a known 1 volt DC so urce and adjos-t
the DC CA L for a full s c a l e d e f l e c ti o n on the m e t e r . A 1. 5 volt batte r y m a y a|io
be used to ca l i bra t e the Field E f f e ct M e t er . Set the Ran ge sw itc h to the 3 vbH
po si ti o n and a d j u s t the m e t er to i nd ic a te 1 . 55 vo lt s which is the nor m a l volta g e
from a new 1. 5 vo lt bat t e ry . A more a c c u r a t e c a l i b r a t i o n may be achiv e d wi » ha
m ercury battery a s it s v ol ta g e i s more c on st an t and h as c l os er t o l e r ance .
Th e Se n c o r e FE1 4 and F E16 F i e ld Effe c t Mete r s use s a ba la nc e d d if f e r e n t ia l a m
pl i f i e r with field e f f e c t tr ans i s t ors ( FET) to pr ov i d e the utmost in tes t m ete r s - the
fl e x a b i l it y and p o r t a b i li t y o f a VOM with a l l the adv an ta g es of a VTV M , high input
imp e d an c e, p e a k to pe a k AC etc.
Fi e l d ef f ect tr a nsi s t ors m a ke this p o s s ib l e , beca u s e e v en though they ar e "so l id
st a t e " they p erfor m like a vacuum tube. T he g a te (gr id ) c o ntro l s the c u r rent flow
betw ee n the s ource (c ath od e) and drain (pla te) by th e ef f ect of the e l ectros t a tic
field betwee n the gate and the source (b ia s ) . T here is n't any gate curren t flow
th e r e f o r e the input imped a nc e i s ex t r e mely high. Sinc e the FET doe s not hav e a
cath od e to "w ea r out " the F ield Ef f e c t Me t e r is mor e sta b l e and les s s u b j e c t to
cha ng e than the c on ve n tio n al VT V M.
TR 1 and T R2 (se e schem a ti c fig. 4) fo r m the d i f f e r e n t i a l am plifi e r used fo r DC
vol ts and Ohms m e a s urem ents. With no volta ge applied to the input of TR 1, the
ZE R O ADJ con tr o l (R3 1 ) is se t so that the volt a g es develop ed across s o u r c e re-,
s i s t ors R 1 4 and R 2 2 are equal, s uch that no cu r ren t will flow thru the m e t e r . " The
CXH B A L co n t r o l (R 2 9) is an int e rn a l adju st m e n t that per f orm s the same a s the
ZE RO AD] c ontrol . It is u sed to c ompens a te f o r com p on en t to l era n ces. When a
DC volt ag e i s applied to the input o f TR1 the bal a n c e be twe en TR 1 and TR2 is up set
and the m e t e r will ind i ca t e in pr o po r ti on to the volt a ge appl ied . Seven DC and AC
ra n ges ar e provid ed with the input d iv id er R 1 thru R 8 . C apa c it ors C2 thr u C8
compen sa t e the divi de r f or AC volt ag e s. The DC· CAL co n tr o l (R 1 5 ) i s an in te r n a l
adj u st m e n t used to c alib r a t e the me ter when a known DC volt ag e i s applie d to the
input. When a very high volt age is applied to the g at e of TRl · (Rang e sw itch se t
in corr e c t l y ) diode CR 7 will condu ct and keep the v olt ag e ap plie d to TR l to a safe
le v el to p r ev e n t des t ructio n o f the tra n sisto r .
Ohm s meas u r e ment s a r e made by fo r m in g a v o lt ag e div id e r with the unknown re
si s tor and a known res ist or - R9 fo r RX1 ran g e, RI O for RX10 r a n g e e t c . - and
rea d in g the voltag e that is developed acro s s the known res i stor. Ini ti a ll y with the
unknown resis t or z e r o (le a d s shor te d to g et he r) the OHMS ADJ c o n t r o l (R2 3 ) is s e t
so that the m e t e r r e a ds at full sc a l e with full poten ti a l fr o m B1 applied to T R l . As
ex t e r nal resista n ce is pla c ed betw een the leads the meter will in d ic a te pro p o r ti o n
at e ly low e r . Th e meter is c a li b r a t e d in oh m s on the top sca l e.
F o r AC volt ag e m e asur e ment s the AC v olt age i s a pp lied to T Rl th r u d ivider R2-R8
as with DC vol ts . Th e output of TRl is fed to a p ea k to p ea k d e t e c t o r c o n s is t i n g
of CIO, Cll, CR1 and CR2. Th e DC output is fed to T R2 thru divi de r R2 5 , R2 6,
R 2 7 and CR6 . The meter is in the so u r c e c i r c uit of TR2. Th e DC volta ge develope d
in the source of TR2, and co n se qu e n tly the .me te r in d ic at io n is pro p o r t io n a l to the
pea k to peak AC applied to T R l . Diodes CR 5 and CR6 co mpen s at e fo r ch a n g es in
te m p e r a t u r e so that meter in di ca ti on s re main accur ate ove r a wide te mper a ture
ran g e .
DC cu r r e nt mea s u r e men ts are made usin g the meter and shunt re sis t ors R16 thru
R1 9 . T h e t r ans i s tors a ndas s ociat e d c i r cui t r y are not used. On the 1 00 m i c ro a mp
ran g e the m e t e r i s co n ne cte d di r e c t l y into the ci r c uit.
Diodes CR 3 and C R 4 pr o t e ct the met e r mo v em e n t fr o m exc e s siv e ov e r l o a d s up to
se vera l am p s . Th e dio de s ar e p r o te c t e d with r esi stor R 24 which wi ll bu r n out
when the ma x im u m curre nt rat in g of the diodes is ex c e e d e d . R 2 4 i s a stand ar d
100 ohm 1/2 wa tt re sis t or.
F IELD EF F ECT METE R TRO UBLE CH AR T
Sym pt om Pro ba b le C au s e C orr e ctive M e a s u r e
Unit dead, m et er De fe c ti ve 9V ba t te r y (B2) Rep l a c e batt e ry
do e s not re a d at al l Poor b a t t e r y con t a ct C heck b atter y contact s
______________________________S hor ted Diode CR3 o r CR 4 Re p l ace de fe c t iv e diode
VOLTS m easu r e men t s ok; Burnt out fu s e r esisto r R24 Re plac e R 24 , 100 ohm s
but no in d ic a ti on on OHMS 1/2 w 10%
and MILLIAMPS functio ns
Can no t ze r o me t e r Fun c tio n and range
RX 1 F u nc t io n in Oh ms
m e asur e men t does not
wor k.
R X 1 0 Fun ct io n in Ohm s
m e asur e men t does not
work .
1 m a functi on only in
current measu r e men ts
do es not w ork .
10 ma funct ion only in
curr e nt mea s u r e men t s
do es not work.
Cann ot adju s t Ohm zer o
to 0
Brok en red w i r e at ON OF F Ch e c k wiri ng to swit ch
swit ch (S3) o r at PC boar d and to PC board
Bro ke n bl a c k wire fr o m C h e c k b l a c k wire
ba t t e ry to PC board
De f e ct i v e M e t e r R e p l ace M e t e r
R eset swi tc h e s to correc t
sw it c h es in cur r e nt
po si t io n s .
Poor co n t a ct at o r/ope n
resi sto r R32
Brok en wir e to z ero adj
con t ro l
T r ansistor s b urnt out
Burnt out re sis t or R9 Re p l ace r e sis t or
Burnt out r esi s tor RIO R e p l a c e r esi sto r
Burnt out r esi s tor Rl6 Repla c e r esi s t or
Burnt out re sis t or R1 7 R e plac e r esisto r
Blue w ir e to ohms ze r o
brok en
Poor con t a c t at batt e ry B1
Broke n wir e to b a t t er y
con ta c t
Weak b a t t er y B1
po s it io n s
R e s older con t a ct and
cha ng e r esi sto r i f n e
c ess ary
Ch e c k wi re to zer o adj
co n t ro l .
R e p l a ce tr ans i s tor s and
reca l ibr ate unit.
Ch e c k for br o ke n wire
Ch e c k for poor c o n t a c ts
Ch e ck wiri ng
R e p l a ce with 1. 5 volt
" C * c ell.
FE 14 SCHEMATIC ISSUE DATE·
R EFERE N C E NO.
PA R T NO. D ES C RI PT IO N
PRIC E
CR1, CR 2, CR 6
CR3, CR4
CR 5
CR 7
M l
R1
R 2
R3
R4
R5
R6
R7
R8
R9
RIO
R ll
R1 5
R1 6
R1 7
R1 8
R19
R2 3
R26
R29
R31
TR l , T R 2
C2
C3 24G1 79 5 6 0 0 P F 5% N 150 . 25
C4
C5 , C9
C6
C1 8
SI
S2
S3
(PR I C E S S U B J E C T TO CHANGE W IT H OU T N OT IC E)
19G2 8A
16G5 Diode rectifier . 5 A
19G 13 Diode, 1N34A .50
50G 2
23C25 B M e t e r 4 1 / 2" , 100 m i c ro a mp
14G271 5 meg 1/2W 1% .75
14G 1 0 3
14G 26 6 23 . 3 K 1/2W 1%
14G2 67 6 6. 7K 1/2W 1%
14G 26 8 233 K 1/2W 1%
14G 26 9
14G 2 70
14G 2 72
14G 26 4 9.1 o hm 1/ 2W 1% .7 5
14G 2 65
14G101
15G6 1 5K c o ntr ol PC Ve r t Mount 1. 50
14G 2 75
14G 27 4
14G27 3
14G 1 4 3
15A 75 15K co nt r o l T a b mount 1" sha f t 1. 50
15G 6 6 1. 2 me g co ntr ol PC Ve r t Mount
15A 53
15A 68
19G2 7 T r ansi st or SS 3 67 2 (FET )
24G 17 3
24G1 74
24G141
24G 1 78
24G 12 0
25A 10 5
25A 10 4
25G4
10 C 2 1 5C
10B 21 6A
10A 2 22 A
33G 1 4 3
33G 2 2 6
35G 16
39G 24
Diode, G e r m a n i u m i
§4 0 0 PIV
Diode S i li co n . 65
1900 ohm coil
10K 1/2W 1%
667 K 1/2W 1%
2. 33 me g 1/2W 1%
6. 67 m e g 1/2W 1%
100 ohm 1/2W 1%
IK 1/2W 1%
220 oh m 1/2W 1%
20 ohm 1/2W 1%
2 ohm 1/2W 1%
8 1/ 4 " Adva nc e wi re
? . 50
1. 50
24. 50
(. 295 oh m s ft)
10K co nt r o l PC Ve r t Mount 1 . 95
50K co n t r ol t ab mount 1" sha ft 1 . 9 5
.01 5 mf 10% m y l a r
21 0 0 PF 5% N150
56 0PF 5% N150
20 0PF 5% N150 . 25
10 MF , 1 5 VO L T S
Ran g e S w it ch 7P12P rotar y $
Fu nc t io n Sw itch 8P4P rot a r y
Slid e S w itc h S PD T
C a s e , vinyl cl a d s t e e l
Panel, sa t i n ch r o me scr e en e d
Ba t t e r y p l a t e (doo r)
Ba t t e r y c l i p ( 1. 5v ”C " c e l l )
Ba t te r y cl a mp (9v olt)
Ba t te r y plug 8" leads
T e st P ro b e with shi eld ed
lead
1 . 9 5
1 . 50
9 .95
8 . 9 5
4. 5 0
3. 2.5
2 .6 0
.75
.75
. 75
.75
.75
.75
. 75
. 75
. 75
. 75
.75
.75
.7 5
. 25
. 25
. 25
. 35
. 50
.5 0
..50
.SO
. I S
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